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46 results on '"Toma, Giuliana"'

1. Measuring the magnetic origins of solar flares, CMEs and Space Weather

Author

Judge, Philip, Rempel, Matthias, Ezzeddine, Rana, Kleint, Lucia, Egeland, Ricky, Berdyugina, Svetlana, Berger, Thomas, Burkepile, Joan, Centeno, Rebecca, de Toma, Giuliana, Dikpati, Mausumi, Fan, Yuhong, Gilbert, Holly, and Lacatus, Daniela

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We take a broad look at the problem of identifying the magnetic solar causes of space weather. With the lackluster performance of extrapolations based upon magnetic field measurements in the photosphere, we identify a region in the near UV part of the spectrum as optimal for studying the development of magnetic free energy over active regions. Using data from SORCE, Hubble Space Telescope, and SKYLAB, along with 1D computations of the near-UV (NUV) spectrum and numerical experiments based on the MURaM radiation-MHD and HanleRT radiative transfer codes, we address multiple challenges. These challenges are best met through a combination of near UV lines of bright \ion{Mg}{2}, and lines of \ion{Fe}{2} and \ion{Fe}{1} (mostly within the $4s-4p$ transition array) which form in the chromosphere up to $2\times10^4$ K. Both Hanle and Zeeman effects can in principle be used to derive vector magnetic fields. However, for any given spectral line the $\tau=1$ surfaces are generally geometrically corrugated owing to fine structure such as fibrils and spicules. By using multiple spectral lines spanning different optical depths, magnetic fields across nearly-horizontal surfaces can be inferred in regions of low plasma $\beta$, from which free energies, magnetic topology and other quantities can be derived. Based upon the recently-reported successful suborbital space measurements of magnetic fields with the CLASP2 instrument, we argue that a modest space-borne telescope will be able to make significant advances in the attempts to predict solar eruptions. Difficulties associated with blended lines are shown to be minor in an Appendix., Comment: Accepted in ApJ, V2 fixed author spelling error

Published
2021
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2. Recent progress on understanding coronal mass ejection/flare onset by a NASA living with a star focused science team

Author

Linton, Mark G., Antiochos, Spiro K., Barnes, Graham, Fan, Yuhong, Liu, Yang, Lynch, Benjamin J., Afanasyev, Andrey N., Arge, C. Nick, Burkepile, Joan, Cheung, Mark C.M., Dahlin, Joel T., DeRosa, Marc L., de Toma, Giuliana, DeVore, C. Richard, Fisher, George H., Henney, Carl J., Jones, Shaela I., Karpen, Judith T., Kazachenko, Maria D., Leake, James E., Török, Tibor, and Welsch, Brian T.

Published
2023
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3. Magnetic nulls and super-radial expansion in the solar corona

Author

Gibson, Sarah E., Dalmasse, Kevin, Rachmeler, Laurel A., De Rosa, Marc L., Tomczyk, Steven, de Toma, Giuliana, Burkepile, Joan, and Galloy, Michael

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Magnetic fields in the sun's outer atmosphere -- the corona -- control both solar-wind acceleration and the dynamics of solar eruptions. We present the first clear observational evidence of coronal magnetic nulls in off-limb linearly polarized observations of pseudostreamers, taken by the Coronal Multichannel Polarimeter (CoMP) telescope. These nulls represent regions where magnetic reconnection is likely to act as a catalyst for solar activity. CoMP linear-polarization observations also provide an independent, coronal proxy for magnetic expansion into the solar wind, a quantity often used to parameterize and predict the solar wind speed at Earth. We introduce a new method for explicitly calculating expansion factors from CoMP coronal linear-polarization observations, which does not require photospheric extrapolations. We conclude that linearly-polarized light is a powerful new diagnostic of critical coronal magnetic topologies and the expanding magnetic flux tubes that channel the solar wind.

Published
2017
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4. COSMO: The COronal Solar Magnetism Observatory

Author

Tomczyk, Steven, primary, Burkepile, Joan, additional, Casini, Roberto, additional, Corchado-Albelo, Marcel, additional, DeLuca, Ed, additional, Toma, Giuliana de, additional, Wijn, Alfred de, additional, Dikpati, Mausumi, additional, Fan, Yuhong, additional, Farid, Samaiyah, additional, Gibson, Sarah, additional, Gilbert, Holly, additional, Judge, Philip, additional, Kucera, Therese, additional, Landi, Enrico, additional, Lin, Haosheng, additional, Martinez-Pillet, Valentin, additional, Morton, Richard, additional, Paraschiv, Alin, additional, Reeves, Katharine, additional, Schad, Thomas A., additional, Seaton, Dan, additional, and Zhang, Jie, additional

Published
2023
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6. Coronal Polarimetry: Determining the Magnetic Origins of Coronal Mass Ejections

Author

Gibson, Sarah E., primary, Bąk-Stęślicka, Urszula, additional, Casini, Roberto, additional, Dahlin, Joel, additional, DeLuca, Edward, additional, Toma, Giuliana de, additional, Fan, Yuhong, additional, Karpen, Judy, additional, Rachmeler, Laurel A., additional, Tomczyk, Steven, additional, Caspi, Amir, additional, Chen, Bin, additional, Corchado-Albelo, Marcel, additional, Farid, Samaiyah, additional, Karna, Nishu, additional, Kucera, Therese, additional, Paraschiv, Alin, additional, Raouafi, Nour E., additional, Schad, Thomas, additional, Seaton, Daniel, additional, Shaik, Shaheda Begum, additional, Wilson, Maurice L., additional, and Zhang, Jie, additional

Published
2023
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7. Observations for Improving SEP Forecasts and Warnings

Author

Burkepile, Joan, primary, Richardson, Ian, additional, Kahler, Stephen, additional, St. Cyr, Orville Christopher, additional, Vourlidas, Angelos, additional, Whitman, Kathryn, additional, Thompson, William, additional, Galloy, Michael, additional, Bain, Hazel, additional, Pevtsov, Alexei, additional, Thompson, Barbara, additional, Cremades, Hebe, additional, Zhang, Jie, additional, Egeland, Ricky, additional, Mays, Leila, additional, Jones, Joycelyn, additional, White, Stephen, additional, Gilbert, Holly, additional, Toma, Giuliana de, additional, Wijn, Alfred de, additional, and Pillet, Valentin, additional

Published
2023
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8. Firefly: The Case for a Holistic Understanding of the Global Structure and Dynamics of the Sun and the Heliosphere

Author

Raouafi, Nour E., primary, Hoeksema, J. Todd, additional, Newmark, Jeffrey S., additional, Gibson, Sarah, additional, Berger, Thomas E., additional, Upton, Lisa A., additional, Vourlidas, Angelos, additional, Hassler, Donald M., additional, Kinnison, James, additional, Ho, George C., additional, Mason, Glenn M., additional, Vievering, Juliana T., additional, Viall, Nicholeen M., additional, Szabo, Adam, additional, Casti, Marta, additional, Case, Anthony W., additional, Lepri, Susan T., additional, Velli, Marco, additional, Georgoulis, Manolis K., additional, Bourouaine, Sofiane, additional, Jagarlamudi, Vamsee K., additional, Laming, John M., additional, Mason, James P., additional, Harra, Louise, additional, Madjarska, Maria, additional, Chitta, Lakshmi Pradeep, additional, Duran, J. Sebastian Castellanos, additional, Korpi-Lagg, Andreas, additional, Badman, Samuel, additional, Chifu, Iulia, additional, Lario, David, additional, Wing, Simon, additional, Bale, Stuart, additional, Paouris, Evangelos, additional, Narayanamurthy, Smitha, additional, Sinjan, Jonas, additional, Bernasconi, Pietro, additional, Krivova, Natalie, additional, Gizon, Laurent, additional, Leamon, Robert J., additional, Gosain, Sanjay, additional, Kazachenko, Maria, additional, Petrie, Gordon, additional, Pillet, Valentin Martinez, additional, Jain, Kiran, additional, Luhmann, Janet, additional, Bertello, Luca, additional, Toriumi, Shin, additional, Jiang, Chen, additional, Vasko, Ivan, additional, Harvey, John W., additional, Schad, Thomas A., additional, Jebaraj, Immanuel C., additional, Scherrer, Philip, additional, Hofmeister, Stefan, additional, Tiwari, Sanjiv, additional, Wang, Haimin, additional, Roth, Markus, additional, Panesar, Navdeep, additional, Sekii, Takashi, additional, Magyar, Norbert, additional, Guglielmino, Salvo L., additional, Parenti, Susanna, additional, Tremblay, Benoit, additional, Tziotziou, Kostas, additional, Toma, Giuliana de, additional, Chen, Bin, additional, Katsukawa, Yukio, additional, Pontieu, Bart De, additional, Cheng, Xin, additional, Cheung, Mark, additional, Kosovichev, Alexander, additional, Jiang, Jie, additional, Schunker, Hannah, additional, Kawabata, Yusuke, additional, Oba, Takayoshi, additional, Cameron, Robert, additional, Mathew, Shibu K., additional, Rodriguez, Jaime de la Cruz, additional, Kusano, Kanya, additional, Temmer, Manuela, additional, Andretta, Vincenzo, additional, Sven, Wedemeyer, additional, Samara, Evangelia, additional, Heinemann, Stephan G., additional, Warmuth, Alexander, additional, Jafarzadeh, Shahin, additional, Mackay, Duncan H., additional, Fludra, Andrzej, additional, Rubio, Luis Bellot, additional, Suárez, David Orozco, additional, Chen, Thomas Y., additional, Kontogiannis, Ioannis, additional, Yardley, Stephanie, additional, Veronig, Astrid, additional, Joshi, Jayant, additional, Spadaro, Daniele, additional, Kubo, Masahito, additional, Bose, Souvik, additional, González, Nazaret Bello, additional, Solanki, Sami, additional, Denker, Carsten, additional, Verma, Meetu, additional, Vocks, Christian, additional, Borrero, Juan Manuel, additional, Mathews, Nathaniel H., additional, Cury, Shannon, additional, Sasso, Clementina, additional, Stenborg, Guillermo, additional, Tibebu, Getachew, additional, Battams, Karl, additional, Wijsen, Nicolas, additional, Bruno, Alessandro, additional, Peter, Hardi, additional, I., Mason Emily, additional, M., Caplan Ronald, additional, Martinez-Sykora, Juan, additional, Seaton, Daniel, additional, Airapetian, Vladimir, additional, Jian, Lan, additional, Thompson, William T., additional, Ofman, Leon, additional, Wallace, Samantha, additional, Kucera, Therese, additional, Desai, Ravindra, additional, Richardson, Ian, additional, Burkepile, Joan, additional, Cranmer, Steven, additional, Strauss, R. Du Toit, additional, Murabito, Mariarita, additional, Alfred, De Wijn, additional, Xie, Hong, additional, Rempel, Matthias, additional, Webber, Shea Hess, additional, Reeves, Katharine K., additional, Hurlburt, Neal, additional, Berrilli, Francesco, additional, DeLuca, Edward, additional, Egeland, Ricky, additional, Ko, Yuan-Kuen, additional, Kee, Nathaniel Dylan, additional, Mahajan, Sushant S., additional, Craig, DeForest, additional, Wood, Brian E., additional, Chris, Chaston, additional, Nigro, Giuseppina, additional, Shaik, Shaheda Begum, additional, Gosic, Milan, additional, Shimizu, Toshifumi, additional, Zuccarello, Francesca, additional, Nitta, Nariaki, additional, Chatzistergos, Theodosios, additional, Fan, Yuhong, additional, Zhang, Jie, additional, Fehlmann, Andre, additional, Palmerio, Erika, additional, Ishikawa, Ryohtaroh T., additional, Danilovic, Sanja, additional, Skan, Moa, additional, Froment, Clara, additional, Baso, Carlos José Díaz, additional, Liang, Zhi-Chao, additional, Wit, Thierry Dudok de, additional, Barczynski, Krzysztof, additional, Johnston, Craig, additional, Pariat, Etienne, additional, Hadid, Lina, additional, Aulanier, Guillaume, additional, Brun, Allan Sacha, additional, Athanasios, Kouloumvakos, additional, Cauzzi, Gianna, additional, Dredger, Pauline, additional, French, Ryan, additional, Christian, Damian, additional, Linton, Mark, additional, Ireland, Jack, additional, Tarr, Lucas, additional, Strugarek, Antoine, additional, Uritsky, Vadim, additional, DeRosa, Marc, additional, Kretzschmar, Matthieu, additional, García, Rafael A., additional, Monteiro, Mario J. P. F. G., additional, Mathur, Savita, additional, Breton, Sylvain N., additional, Pinto, Rui F., additional, Oliveros, Juan Carlos Martinez, additional, Loper, Robert, additional, Auchère, Frédéric, additional, Wang, Tongjiang, additional, Reginald, Nelson, additional, Cunha, Margarida S., additional, Teriaca, Luca, additional, Chintzoglou, Georgios, additional, Lynch, Benjamin J., additional, Linker, Jon, additional, Beck, Paul, additional, Shannon, Jackson, additional, Clare, Benjamin, additional, Krupiarz, Christopher, additional, Whiting, Ian D., additional, Byerly, Adam, additional, Bushman, Stewart, additional, Carrelli, David, additional, Kijewski, Seth, additional, Englander, Jacob, additional, Mizes, Adam, additional, Porter, Jamie, additional, O’Neill, Michael, additional, Chattopadhyay, Debarati, additional, Albers, Joshua, additional, Rast, Mark, additional, Ermolli, Ilaria, additional, Tzeng, Nigel, additional, Hudson, James F., additional, Giunta, Alessandra, additional, Buchlin, Éric, additional, Bommier, Véronique, additional, Duncan, Nicole, additional, Janvier, Miho, additional, Strecker, Hanna, additional, Siu, Azaymi, additional, Perri, Barbara, additional, Maksimovic, Milan, additional, Vilmer, Nicole, additional, Toledo-Redondo, Sergio, additional, Kuckein, Christoph, additional, Alberti, Tommaso, additional, Antolin, Patrick, additional, Cuadrado, Regina Aznar, additional, Berghmans, David, additional, Brigitte, Schmieder, additional, Bucik, Radoslav, additional, Calchetti, Daniele, additional, Caspi, Amir, additional, Cohen, Christina, additional, Corbard, Thierry, additional, Cremades, Hebe, additional, Cummings, Alan, additional, Dhakal, Suman, additional, Dolla, Laurent, additional, Dominique, Marie, additional, Emslie, Gordon, additional, Ferrente, Fabiana, additional, Finley, Adam J., additional, Fletcher, Lyndsay, additional, Fraschetti, Federico, additional, Gafeira, Ricardo, additional, Gissot, Samuel, additional, Hegde, Dinesha, additional, Hu, Qiang, additional, Innocenti, Maria Elena, additional, Jin, Meng, additional, Klein, Kristopher, additional, Kumar, Pankaj, additional, Lacatus, Daniela, additional, Liewer, Paulett, additional, Magdalenic, Jasmina, additional, Mandal, Sudip, additional, Mandrini, Cristina H., additional, Mierla, Marilena, additional, Miralles, Mari Paz, additional, Moore, Ron, additional, Neville, Jonathan, additional, Niembro, Tatiana, additional, Nikou, Eleni, additional, Nindos, Alexander, additional, Papaioannou, Athanasios, additional, Rajaguru, S. Paul, additional, Reville, Victor, additional, Rochus, Pierre, additional, Rodriguez, Luciano, additional, Romoli, Marco, additional, Shestov, Sergei, additional, Shi, Chen, additional, Sorriso-Valvo, Luca, additional, St. Cyr, O. C., additional, Sterling, Alphohse, additional, Stevens, Michael L., additional, Susino, Roberto, additional, Swisdak, Marc, additional, Thompson, Barbara J., additional, Valliappan, Senthamizh Pavai, additional, Verbeeck, Francis, additional, Bothmer, Volker, additional, Xudong, Sun, additional, Zhukov, Andrei, additional, Katsiyannis, Thanassis, additional, Owen, Christopher, additional, Karna, Nishu, additional, Janssens, Jan, additional, Khomenko, Elena, additional, Gary, Dale, additional, Bandyopadhyay, Riddhi, additional, Chhiber, Rohit, additional, Tenerani, Anna, additional, Rouillard, Alexis, additional, Patsourakos, Spiros, additional, Anastasiadis, Anastasios, additional, Bocchialini, Karine, additional, Moraitis, Kostas, additional, Rivera, Yeimy, additional, Drake, James, additional, Baudin, Frédéric, additional, Chandran, Benjamin, additional, Dayeh, Maher, additional, Reardon, Kevin, additional, Cairns, Iver, additional, Bizien, Nina, additional, Wexler, David, additional, Bahauddin, Shah, additional, Rodriguez-Pacheco, Javier, additional, Yu, Sijie, additional, Lee, Jeongwoo, additional, Gontikakis, Costis, additional, Koukras, Alexandros, additional, Contel, Olivier Le, additional, Pezzi, Oreste, additional, Kintziger, Christian, additional, Boumier, Patrick, additional, Balasis, Georgios, additional, Dikpati, Mausumi, additional, Pesnell, W. Dean, additional, Chai, Yi, additional, Nandy, Dibyendu, additional, Charles, Arge, additional, Corti, Claudio, additional, Zhao, Lulu, additional, Matthaeus, William H., additional, Gilly, Chris R., additional, Erlandson, Robert E., additional, Derouich, Moncef, additional, Zhao, Lingling, additional, Poedts, Stefaan, additional, Vieira, Luis, additional, Adhikari, Laxman, additional, Buitrago-Casas, Juan Camilo, additional, Huang, Jia, additional, Moestl, Christian, additional, Liu, Mingzhe, additional, Oloketuyi, Jacob, additional, Zhuang, Bin, additional, Rodríguez-García, Laura, additional, Perez, Jean Carlos, additional, Xu, Zigong, additional, Kooi, Jason, additional, Woodham, Lloyd D., additional, Tripathi, Durgesh, additional, Young, Peter, additional, López-Portela, Cynthia, additional, Cuesta, Manuel Enrique, additional, and Wilson, Lynn, additional

Published
2023
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14. A Mosaic of the Inner Heliosphere: Three Carrington Rotations During the Whole Heliosphere and Planetary Interactions Interval.

Author

Allen, Robert C., Gibson, Sarah E., Hewins, Ian, Vines, Sarah K., Qian, Liying, de Toma, Giuliana, Thompson, Barbara J., Hudson, Mary, Lee, Christina O., Filwett, Rachael J., Mostafavi, Parisa, Mo, Wenli, and Hill, Matt E.

Subjects
HELIOSPHERE, SOLAR oscillations, SOLAR wind, ROTATIONAL motion, MAGNETIC storms
Abstract

The Whole Heliosphere and Planetary Interactions initiative was established to leverage relatively quiet intervals during solar minimum to better understand the interconnectedness of the various domains in the heliosphere. This study provides an expansive mosaic of observations spanning from the Sun, through interplanetary space, to the magnetospheric response and subsequent effects on the ionosphere‐thermosphere‐mesosphere (ITM) system. To accomplish this, a diverse set of observational datasets are utilized from 2019 July 26 to October 16 (i.e., over three Carrington rotations, CR2220, CR2221, and CR2222) with connections of these observations to the more focused studies submitted to this special issue. Particularly, this study focuses on two long‐lived coronal holes and their varying impact in sculpting the heliosphere and driving of the magnetospheric system. As a result, the evolution of coronal holes, impacts on the inner heliosphere solar wind, glimpses at mesoscale solar wind variability, magnetospheric response to these evolving solar wind drivers, and resulting ITM phenomena are captured to reveal the interconnectedness of this system‐of‐systems. Plain Language Summary: The field of Heliophysics research spans a large range of plasma regimes and disciplines that are all linked through the complex interactions each system has with one another. To better explore the interconnected nature of the heliosphere, this study combines observations from across the sub‐domains of Heliophysics to construct snapshots of the Sun, solar wind, and the magnetospheric and ionospheric systems at Earth over three revolutions of the Sun. This allows for a unique vantage point to put these systems in perspective of one another and understand how they impact one another. Key Points: The evolution and impacts of two coronal holes are investigated over three Carrington rotationsThe evolution of the coronal hole led to changes in the solar wind throughout the inner solar systemSubsequent geospace response differed with each passage due to both changes in the solar wind and preconditioning within the systems [ABSTRACT FROM AUTHOR]

Published
2023
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16. Measuring the Magnetic Origins of Solar Flares, Coronal Mass Ejections, and Space Weather

Author

Judge, Philip, primary, Rempel, Matthias, additional, Ezzeddine, Rana, additional, Kleint, Lucia, additional, Egeland, Ricky, additional, Berdyugina, Svetlana V., additional, Berger, Thomas, additional, Bryans, Paul, additional, Burkepile, Joan, additional, Centeno, Rebecca, additional, de Toma, Giuliana, additional, Dikpati, Mausumi, additional, Fan, Yuhong, additional, Gilbert, Holly, additional, and Lacatus, Daniela A., additional

Published
2021
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17. A Snapshot of the Sun Near Solar Minimum: The Whole Heliosphere Interval

Author

Thompson, Barbara J., Gibson, Sarah E., Schroeder, Peter C., Webb, David F., Arge, Charles N., Bisi, Mario M., de Toma, Giuliana, Emery, Barbara A., Galvin, Antoinette B., Haber, Deborah A., Jackson, Bernard V., Jensen, Elizabeth A., Leamon, Robert J., Lei, Jiuhou, Manoharan, Periasamy K., Mays, M. Leila, McIntosh, Patrick S., Petrie, Gordon J. D., Plunkett, Simon P., Qian, Liying, Riley, Peter, Suess, Steven T., Tokumaru, Munetoshi, Welsch, Brian T., and Woods, Thomas N.

Published
2011
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23. Forward Modeling of a Pseudostreamer

Author

Karna, Nishu, primary, Savcheva, Antonia, additional, Dalmasse, Kévin, additional, Gibson, Sarah, additional, Tassev, Svetlin, additional, Toma, Giuliana de, additional, and DeLuca, Edward E., additional

Published
2019
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28. Solar Cycle 23: An Unusual Solar Minimum?

Author

de Toma, Giuliana, primary, Gibson, Sarah, additional, Emery, Barbara, additional, Kozyra, Janet, additional, Maksimovic, M., additional, Issautier, K., additional, Meyer-Vernet, N., additional, Moncuquet, M., additional, and Pantellini, F., additional

Published
2010
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33. Solar Cycle 23: An Anomalous Cycle?

Author

de Toma, Giuliana, primary, White, Oran R., additional, Chapman, Gary A., additional, Walton, Stephen R., additional, Preminger, Dora G., additional, and Cookson, Angela M., additional

Published
2004
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35. Solar Cycle 23: An Unusual Solar Minimum?

Author

de Toma, Giuliana, Gibson, Sarah, Emery, Barbara, and Kozyra, Janet

Subjects
*SOLAR cycle, *STELLAR winds, *SOLAR wind, *SOLAR activity, *SOLAR magnetic fields
Abstract

We are currently observing the minimum phase of Cycle 23. Magnetic activity during the years 2006–2009 has been very weak with sunspot numbers reaching the lowest values in about 100 years. This long and extended minimum is characterized by weak polar magnetic fields, small polar coronal holes, and a relatively complex coronal morphology. This magnetic configuration at the Sun is remarkably different from the one observed during the previous two solar minima. We review observations made at the Sun and in the solar wind during the recent solar minima and discuss the implications of the observed differences for the heliosphere and geospace. [ABSTRACT FROM AUTHOR]

Published
2010
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40. Effect of Spectral Resolution on the Mg II Index as a Measure of Solar Variability.

Author

White, Oran, De Toma, Giuliana, Rottman, Gary, Woods, Thomas, and Knapp, Barry

Abstract

The solar Mgii core-to-wing ratio is a useful index of UV variability throughout the solar cycle because it has been measured since 1978 in a series of successive satellite missions: Nimbus 7, Solar Mesosphere Explorer (SME), the NOAA 9–14 series, Upper Atmosphere Research Satellite (UARS), and ERS-2. Eventual construction of a single time series from 1978 to the present by combining these measurements will give a long record of almost daily UV variability to serve as a surrogate for estimating both UV and EUV solar radiation. Here we address the effect of spectral resolution on determination of both long-term and short-term solar variability from this index. We use UARS/SOLSTICE measurements of the Mgii line from October 1991 to December 1996 to study the effect of two spectral resolution regimes characteristic of existing measurements, 0.20 to 0.25 nm and 1.10 to 1.15 nm, on determination of the amplitude of 27-day rotational modulation and the more gradual change in chromospheric radiation in the declining phase of solar cycle 22. The two Mgii indices give solar variations that differ by a scaling factor of ≈ 2× for both the solar cycle change from 1992 to 1997 and the amplitude of 27-day modulation over the same period. Both types of measurements appear to yield solar signal equally well except at solar minimum when the solar changes become quite small. [ABSTRACT FROM AUTHOR]

Published
1998
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43. Solar Cycle 23: An Anomalous Cycle?

Author

Toma, Giuliana de, White, Oran R., Chapman, Gary A., Walton, Stephen R., Preminger, Dora G., and Cookson, Angela M.

Abstract

The latest SOHO VIRGO total solar irradiance (TSI) time series is analyzed using new solar variability measures obtained from full-disk solar images made at the San Fernando Observatory and the Mg II 280 nm index. We discuss the importance of solar cycle 23 as a magnetically simpler cycle and a variant from recent cycles. Our results show the continuing improvement in TSI measurements and surrogates containing information necessary to account for irradiance variability. Use of the best surrogate for irradiance variability due to photospheric features (sunspots and faculae) and chromospheric features (plages and bright network) allows fitting the TSI record to within an rms difference of 130 ppm for the period 1986 to the present. Observations show that the strength of the TSI cycle did not change significantly despite the decrease in sunspot activity in cycle 23 relative to cycle 22. This points to the difficulty of modeling TSI back to times when only sunspot observations were available.

Published
2004

44. A Picture of Solar Minimum and the Onset of Solar Cycle 23. I. Global Magnetic Field Evolution

Author

Toma, Giuliana de, White, Oran R., and Harvey, Karen L.

Abstract

NSO/Kitt Peak synoptic charts of magnetic flux in the period from 1996 to 1998 are analyzed together with time series for the 10.7 cm radio flux, sunspot number, and Mg II chromospheric index to determine the origin of the two times of minimum activity in 1996 and to study their relationships in the ascending phase of solar cycle 23. The solar activity minima in February-April and September-November of 1996 are found to correspond to periods of low magnetic activity in the southern and northern solar hemispheres, respectively. The new solar cycle becomes dominant in early 1997, but it is only in the summer of 1997 that a significant increase can be detected in the magnetic fields observations as well as in irradiance data, and by the end of 1998, the activity level has increased to a value comparable to the one observed in 1993. Using the magnetic synoptic charts, we determine the number of persistent longitude bands of active nests during this rising phase of solar cycle 23. We find an increase in the number of active nests from zero in 1996 to three by 1998. We speculate that these persistent bands of flux emergence correspond to a pattern of low-order modes of instability of the type found in the theoretical work of Gilman, Fox, and Dikpati on joint instability of latitudinal differential rotation and toroidal magnetic fields at the base of the convection zone. We argue that the observed increase in the number of active nests is consistent with the increase in the longitudinal wavenumber of magnetic instabilities in a concentrated toroidal field in the tachocline discussed in 1999 by Gilman and Dikpati.

Published
2000

45. Long-Term Variation of the Interplanetary H Ly? Glow: VoyagerUVS Measurements and Implications for the Solar H Ly? Irradiance

Author

de Toma, Giuliana, Quémerais, Eric, and Sandel, Bill R.

Abstract

In this paper we study interplanetary (IP) Ly? data taken with the Voyager1and Voyager2spacecraft from 1980 to 1995. The coverage in time is equal to about 156 and 220 points yr-1for Voyager1and Voyager2, respectively, with almost no gaps. The IP Ly? data are normalized for spatial changes in the emissivity, which arise from variations in observing geometry, by using a radiative transfer model. The normalized data show the variation of the solar H Ly? line-center flux during the solar cycle. We compare this variation with the solar H Ly? irradiance measurements of integrated flux from the SolarMesosphereExplorerand the UpperAtmosphereResearchSatellite/Solar-Stellar Irradiance Comparison Experiment (SOLSTICE), and, when direct solar measurements are not available, we use estimated irradiances from magnesium and helium indices. The comparison between VoyagerIP data and solar data shows that the best agreement is found with the SOLSTICE set of measurements, when no differences in the variation of the line-center flux and the integrated flux are taken into account.

Published
1997
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