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Orbit spin coupling is proposed as an alternative to planetary tidal models for the excitation of solar variability as a function of time. Momentum sourced from the orbital angular momenta of solar system bodies is deposited within the circulating fluid envelopes of the Sun and planets in this hypothesis. A reversing torque acts about an axis lying within the Sun's equatorial plane. The torque gives rise to tangential differential accelerations of solar materials as a function of longitude, latitude, depth, and time. The accelerations pulse in amplitude, and change sign, on timescales corresponding to the periods, beats, and harmonics of inner and outer planet orbital motions. In contrast to planetary tidal models, no special amplification mechanism may be required, as estimated peak accelerations are about 2 orders of magnitude larger than the largest tidal accelerations. Organized mass motions driven by the torque may be incorporated in dynamo simulations through the flow velocity term of the MHD induction equation. The spatiotemporal variability of flow velocities may then influence the variability with time of solar magnetic activity. We provide torque values at 1 day timesteps for the years 1660 to 2220. We discuss the time variability of the torque in juxtaposition with SIDC monthly sunspot numbers from 1750 to present. We investigate Hale cycle synchronization, and the variability with time of the total solar irradiance, with reference to outer and inner planet contributions respectively. We propose a 3 component model for understanding and simulating the solar magnetic cycle, which includes processes internal to the Sun, external forcing, due to orbit spin coupling, and a time-delay, or system memory, component. This model supplies a physical explanation for the observed variability with time of Schwabe cycle periods and Hale cycle periods from 1712 to present., Comment: 95 pages, 8 Figures

The recent addition of orbit-spin coupling torques to atmospheric global circulation models has enabled successful years-in-advance forecasts of global and regional-scale dust storms on Mars. Here we explore the applicability of the orbit-spin coupling mechanism for understanding and forecasting anomalous weather and climate events on Earth. We calculate the time history of orbit-spin coupling torques on the Earth system for the interval from 1860-2040. The torque exhibits substantial variability on decadal to bidecadal timescales. Deep minima recur at intervals from 15-26 years; eight such episodes are documented within the study period prior to 2020. Each of the identified torque minima corresponds in time to an episode of widespread drought in the Western USA extending over several years. The multiyear droughts of the 1930s, the 1950s, the mid-1970s, the early 1990s, and of 2011-2015 were each coincident in time with orbit-spin coupling torque minima. The upcoming torque minimum of 2030 is the deepest such minimum of the 180-yr study interval. A multiyear episode of widespread drought in the Western USA is likely to be underway by 2028 plus or minus 4 years (2 standard deviations). The potential benefits to societies of improved drought predictions justify an immediate high-priority effort to include forcing by orbit-spin coupling within state-of-the-art Earth system GCMs. Future targeted numerical modeling investigations are likely to yield forecasts with considerably lower uncertainties and with much improved temporal resolution in comparison to that obtained here.

The orbital motions and spin-axis rotations of extended bodies are traditionally considered to be coupled only by tidal mechanisms. The orbit-spin coupling hypothesis supplies an additional mechanism. A reversing torque on rotating extended bodies is identified. The torque effects an exchange of angular momentum between the reservoirs of the orbital and rotational motions. The axis of the torque is constrained to lie within the equatorial plane of the subject body. Hypothesis testing to date has focused on the response to the putative torque of the Martian atmosphere. Atmospheric global circulation model simulations reveal that an episodic strengthening and weakening of meridional overturning circulations should be observable and is diagnostic in connection with the triggering of Martian planet-encircling dust storms. Spacecraft observations obtained during the earliest days of the 2018 Martian global dust storm document a strong intensification of atmospheric meridional motions as predicted under this hypothesis. We review implications for atmospheric physics, for investigations of planetary orbital evolution with rotational energy dissipation, and for theories of gravitation.

Orbit-spin coupling torques on the Earth in November 2020 are larger than at any other time between 2000 and 2050. This affords an opportunity to observe the terrestrial atmospheric response to the putative torque in near real time., Comment: 4 pages 1 figure

We explore consequences for the solar dynamo of a newly-developed physical hypothesis describing a weak coupling of the orbital and rotational motions of extended bodies. The coupling is given by - c ((dL/dt) x omega sub alpha) x r, where dL/dt represents the rate of change of barycentric orbital angular momentum, omega sub alpha is the angular velocity of rotation, r is a position vector identifying a particular location in a coordinate system rotating with the Sun, and c is a coupling efficiency coefficient. This form of coupling has no dependence on tides. The coupling expression defines a non-axisymmetric global-scale acceleration field that varies both in space and with time. Meridional components of acceleration typically dominate in equatorial and middle latitudes, while zonal accelerations become increasingly significant at higher latitudes. A comparison of the waveform of the putative dynamical forcing function with the time series for measured solar meridional flow speeds from Sunspot Cycle 23 yields correlations significant at the 99.9% level. We introduce the possibility of a destructive interaction between the predicted large-scale flows (due to orbit-spin coupling) and the dynamo mechanism(s) of the 22-year magnetic activity cycle; observations in recent cycles of higher meridional flow speeds during episodes of reduced solar sunspot activity may be explained as a consequence of differences between the phasing of the magnetic cycle and the phase of the forcing function. Algorithms are provided for calculating meridional and zonal orbit-spin coupling accelerations within the Sun as a function of latitude, longitude, depth, and time., Comment: 70 pages, 5 figures

The physical origins of the observed interannual variability of weather and climate on Mars are poorly understood. In this paper we introduce a deterministic physical mechanism that may account for much of the variability of the circulation of the Mars atmosphere on seasonal and longer timescales. We derive a coupling expression linking orbital and rotational motions that produces an acceleration field varying with position and with time on and within a subject body. The spatially and temporally varying accelerations may interfere constructively or destructively with large-scale flows of geophysical fluids that are established and maintained by other means. The hypothesis predicts cycles of intensification and relaxation of circulatory flows of atmospheres on seasonal and longer timescales that are largely independent of solar forcing. The predictions of the hypothesis may be tested through numerical modeling. Examples from investigations of the atmospheric circulation of Mars are provided to illustrate qualitative features and quantitative aspects of the mechanism proposed. We briefly discuss the implications and applicability of the orbit-spin coupling hypothesis for planets other than Mars., Comment: 59 pages, 6 figures, 3 appendices

A new physical hypothesis predicts that a weak coupling of the orbital and rotational motions of extended bodies may give rise to a modulation of circulatory flows within their atmospheres. Driven cycles of intensification and relaxation of large-scale circulatory flows are predicted, with the phasing of these changes linked directly to the rate of change of the orbital angular momentum with respect to inertial frames. We test the hypothesis that global-scale dust storms (GDS) on Mars may occur when periods of circulatory intensification (associated with positive and negative extrema of the waveform) coincide with the southern summer dust storm season on Mars. The orbit-spin coupling hypothesis additionally predicts that the intervening transitional periods, which are characterized by the disappearance and subsequent sign change of this waveform, may be unfavorable for the occurrence of GDS, when they occur during the southern summer dust storm season. These hypotheses are confirmed through comparisons between calculated dynamical time series of the time rate of change of orbital angular momentum and historic observations. All of the nine known global-scale dust storms on Mars took place during Mars years when circulatory intensification during the dust storm season is predicted under the orbit-spin coupling hypothesis. No historic global-scale dust storms were recorded during transitional intervals. Orbit-spin coupling accelerations evidently contribute to the interannual variability of the Mars atmosphere., Comment: 44 pages, 7 figures

We employ the MarsWRF general circulation model (GCM) to test the predictions of a new physical hypothesis: a weak coupling of the orbital and rotational angular momenta of extended bodies is predicted to give rise to cycles of intensification and relaxation of circulatory flows within atmospheres. The dynamical core of the GCM has been modified to include the orbit-spin coupling accelerations due to solar system dynamics for the years 1920-2030. The modified GCM is first subjected to extensive testing and validation. We compare forced and unforced model outcomes for large-scale zonal and meridional flows, and for near-surface wind velocities and surface wind stresses. The predicted cycles of circulatory intensification and relaxation within the modified GCM are observed. Most remarkably, the modified GCM reproduces conditions favorable for the occurrence of perihelion-season global-scale dust storms on Mars in years in which such storms were observed. A strengthening of the meridional overturning (Hadley) circulation during the dust storm season occurs in the GCM in all previously known years with perihelion-season global-scale dust storms. The increased upwelling produced in the southern hemisphere in southern summer may facilitate the transport of dust to high altitudes in the Mars atmosphere during the dust storm season, where radiative heating may further strengthen the circulation. Significantly increased surface winds and surface wind stresses are also obtained. These may locally facilitate saltation and dust lifting from the surface. The numerical simulations constitute proof of concept for the orbit-spin coupling hypothesis under evaluation., Comment: 68 pages, 22 figures, 6 tables and 23 supplemental figures

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