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This study examines the variation of different energies linked with the Sun and the Earth’s magnetosphere-ionosphere systems for solar cycles (SCs) 22–24 for which the gradual decrease in the solar activity is noticed. Firstly, we investigated the variation of solar magnetic energy density (SMED) for SCs 21–24 and its relation to the solar activity. We observed distinct double peak structures in SMED for the past four SCs, 21–24. This feature is consistent with noticeable asymmetry in their two peaks. For SCs 22–24 a significant decrease is observed in the integrated SMED of each SC. This reduction is 37% from SCs 22 to 23 and 51% from SCs 23 to 24, which indicates substantial weakening of Sun’s magnetic field for SC 24. Also, the magnetic, kinetic, and thermal energy densities at the Earth’s bow-shock nose are found to be considerably low for the SC 24. We examined the solar wind Alfven speed, magnetosonic Mach number, solar wind-magnetosphere energy coupling parameter (ε), and the Chapman-Ferraro magnetopause distance (LCF) for the SCs 22–24. The estimated maximum stand-off magnetopause distance is larger for SC 24 (LCF ≤ 10.6 RE) as compared to SC 23 (LCF ≤ 10.2 RE) and SC 22 (LCF ≤ 9.8 RE). The solar wind Alfven speeds during SCs 22 and 23 are in the same range and do not exceed ≈73 km/s whereas, it is below 57 km/s for SC 24. A lower bound of solar wind magnetosonic Mach number for SC 24 is larger (M ≥ 6.9) as compared to SC 22 (M ≥ 5.9) and SC 23 (M ≥ 6). We noticed weakening in the energy coupling parameter for SC 24, which resulted in substantial (15%–38%) decrease in average strength of high latitude ionospheric (AE), low latitude magnetospheric (Dst) and equatorial ionospheric (EEJ) current systems in comparison with SC 23. Subsequently, a reduction of ≈30% is manifested in the high latitude Joule heating for SC 24. Overall this study indicates the significant step down in various energies at Sun, Earth’s bow-shock, and near Earth environment for current SC 24, which will have important implication on our Earth’s atmosphere-ionosphere-magnetosphere system.

It is shown that during the 30 October 2003 superstorm, dayside O+ ions were uplifted to DMSP altitudes (~850 km). Peak densities were ~9 × 105 cm−3 during the magnetic storm main phase (peak Dst = −390 nT). By comparison the 1–2 September 1859 Carrington magnetic storm (peak Dst estimated at −1760 nT) was considerably stronger. We investigate the impact of this storm on the low- to mid-latitude ionosphere using a modified version of the NRL SAMI2 ionospheric code. It is found that the equatorial region (LAT = 0° ± 15°) is swept free of plasma within 15 min (or less) of storm onset. The plasma is swept to higher altitudes and higher latitudes due to E × B convection associated with the prompt penetration electric field. Equatorial Ionization Anomaly (EIA) O+ density enhancements are found to be located within the broad range of latitudes ~ ± (25°–40°) at ~500–900 km altitudes. Densities within these peaks are ~6 × 106 oxygen ions-cm−3 at ~700 km altitude, approximately +600% quiet time values. The oxygen ions at the top portions (850–1000 km) of uplifted EIAs will cause strong low-altitude satellite drag. Calculations are currently being performed on possible uplift of oxygen neutrals by ion-neutral coupling to understand if there might be further significant satellite drag forces present.

Updated summaries of the August 1972 and March 1989 space weather events have been constructed. The features of these two events are compared to the Carrington 1859 event and a few other major space weather events. It is concluded that solar active regions release energy in a variety of forms (X‐rays, EUV photons, visible light, coronal mass ejection (CME) plasmas and fields) and they in turn can produce other energetic effects (solar energetic particles (SEPs), magnetic storms) in a variety of ways. It is clear that there is no strong one‐to‐one relationship between these various energy sinks. The energy is often distributed differently from one space weather event to the next. Concerning SEPs accelerated at interplanetary CME (ICME) shocks, it is concluded that the Fermi mechanism associated with quasi‐parallel shocks is relatively weak and that the gradient drift mechanism (electric fields) at quasi‐perpendicular shocks will produce harder spectra and higher fluxes. If the 4 August 1972 intrinsic magnetic cloud condition (southward interplanetary magnetic field instead of northward) and the interplanetary Sun to 1 au conditions were different, a 4 August 1972 magnetic storm and magnetospheric dawn‐to‐dusk electric fields substantially larger than the Carrington event would have occurred. Under these special interplanetary conditions, a Miyake et al. (2012), https://doi.org/10.1038/nature11123‐like extreme SEP event may have been formed. The long duration complex 1989 storm was probably greater than the Carrington storm in the sense that the total ring current particle energy was larger. Plain Language Summary: All the main information for the August 1972 and March 1989 space weather events have been gathered together for the readership. Various features of these two events have been compared and contrasted to the Carrington event and several other recent major events. It is thought that major energetic MeV to GeV particle acceleration occurs at interplanetary shocks instead of acceleration at the solar flare site. Two popular mechanisms for shock particle acceleration are: (a) Fermi acceleration between waves upstream and downstream of a shock, and (b) particle gradient drift in the direction of an electric field along the shock surface. The second mechanism is concluded to form a harder particle spectrum with higher fluxes. If the intrinsic conditions of the 4 August 1972 coronal mass ejection were different (southward interplanetary magnetic fields) and that propagated to the Earth without major evolution or distortion, a magnetic storm equal to or more intense than the Carrington event would have occurred. We have also constructed a scenario involving altered interplanetary space for the August 1972 event which could lead to a high Mach number quasiperpendicular shock and possibly a solar particle event comparable to the Miyake et al. (2012, https://doi.org/10.1038/nature11123) tree ring event. Key Points: The August 1972 and March 1989 space weather events are summarized and compared to the Carrington plus a few other recent eventsWith different solar and interplanetary conditions, the August 1972 ICME could have caused a storm greater than the Carrington stormThe complex March 1989 storm was a "stealth magnetic storm", probably greater ring‐current energy‐wise than the Carrington storm [ABSTRACT FROM AUTHOR]

The North American Aerospace Defense Command (NORAD) tracking of the SpaceX Starlink satellite launch on 2022 February 3 is reviewed. Of the 49 Starlink satellites released into orbit, 38 were eventually lost. Thirty-two of the satellites were never tracked by NORAD. Two different physical mechanisms have been proposed published in Space Weather and one in arXiv to explain the satellite losses. It is argued that none of these three papers can explain the immediate loss of 32 of the 49 satellites. We suggest NORAD satellite tracking information for scientists to further investigate possible loss mechanisms. [ABSTRACT FROM AUTHOR]

Intense, midnight‐to‐dawn sector, near‐equatorial, chorus rising tones which cross frequencies of ∼0.5fce $\sim 0.5{f}_{\text{ce}}$ have been analyzed to determine their structures and possible substructures. Upper band (f≥0.5fce $f\ge 0.5{f}_{\text{ce}}$) chorus and "gap" (f∼0.5fce $f\sim 0.5{f}_{\text{ce}}$) chorus are examined in detail for the first time. It is found that upper band chorus and gap chorus are composed of the same structure as lower band (f≤0.5fce $f\le 0.5{f}_{\text{ce}}$) chorus: they are composed of short‐duration subelements, which are monochromatic with σ≤1% $\sigma \le 1\%$. These findings have strong implications for the chorus element generation mechanism. Following Kennel and Petschek (1966, https://doi.org/10.1029/JZ071i001p00001) the overall chorus riser is most likely generated by anisotropic (T⊥/T∥ ${T}_{\perp }/{T}_{{\Vert} }$ > 1) ∼10–100 keV substorm‐injected electrons. Assuming cyclotron resonance, the upper band chorus is generated by the low energy portion of the electron spectrum. The often‐present gap at ∼0.5fce $\sim 0.5{f}_{\text{ce}}$ is related to Landau/cyclotron damping. This however is not the end of the story. There is another type of two‐frequency chorus (called Type 2) for which the lower band is not well connected to the upper band. A Type 2 chorus reported previously by Fu et al. (2014, https://doi.org/10.1002/2014JA020364) has also been studied in detail. Both the lower band and upper band are composed of subelements which are monochromatic. Such a similar fine structure for the different type of chorus may imply a similar generation mechanism, for which the difference between them is just the energy range of resonant energetic electrons. One mechanism discussed here, generation by phase bunched electrons, will be tested in the near future. Plain Language Summary: Understanding chorus structure and microstructure is essential toward understanding the wave generation mechanisms and wave‐particle interaction consequences. In this paper we show that upper band (f≥0.5fce $f\ge 0.5{f}_{\text{ce}}$) chorus and gap chorus (f∼0.5fce $f\sim 0.5{f}_{\text{ce}}$) are composed of substructures (subelements) which are monochromatic with σ≤1% $\sigma \le 1\%$. These are the same features of lower band (f≤0.5fce $f\le 0.5{f}_{\text{ce}}$) chorus. The Kennel‐Petschek theory therefore needs to be enlarged such that phase‐bunching of ∼10–100 keV substorm injected anisotropic electrons occur, which then "lase" to yield the monochromatic wave subelements. Coherent and monochromatic chorus can explain the rapid burstiness of ionospheric microburst X‐ray structures. There is another type of upper band chorus, called Type 2 upper band chorus, where the lower band chorus elements are not clearly connected to the upper band chorus. A Type 2 chorus reported previously by Fu et al. (2014, https://doi.org/10.1002/2014JA020364) has been examined in this paper. The apparently unrelated upper band has been found to be composed of subelements which are monochromatic in nature. Thus the different type of chorus may be excited by a similar generation mechanism, for which the difference between them is only the energy interval of the resonant energetic electrons. Key Points: Type 1 upper band chorus and gap chorus are found to be composed of short duration subelements which are monochromatic (σ≤1% $\sigma \le 1\%$)Since all parts of chorus risers have similar constructions, it is most probable that they are generated by anisotropic narrow energy‐range phase‐bunched electronsA Type 2 chorus (no connection between the lower band and upper band) was studied. The upper band was composed of monochromatic subelements [ABSTRACT FROM AUTHOR]

Dromions are exact nonlinear solutions of a large class of two-dimensional (2-D) partial differential equations and may he considered as an extension of the familiar soliton solutions to the 2-D space. They have stable localized structures with an exponential decay in both space dimensions and are characterized by time-dependent boundary conditions. While solitons have been used extensively to model coherent wave phenomena in plasmas, dromions have received little attention in terms of application to experimental observations. In a recent paper, we have shown that the nonlinear evolution of a 2-D electron acoustic wave in auroral plasma may lead to dromion solutions whose shape and size can he consistent with those of monopolar and bipolar pulses observed by the high resolution measurements of POLAR and FAST satellites. The previous theoretical analysis is extended to examine the time evolution of the dromion solution, study its stability, and discuss its boundary conditions in the context of auroral plasmas. The effect of different parameters on the shape and size of the dromion solutions is also estimated. Index Terms--Auroral plasma, dromion, electron acoustic wave, solitary wave.