[1] It is now well established that many bulk properties of the solar wind rise and fall with the solar cycle, and the heliospheric magnetic field (HMF) intensity is no exception. The HMF intensity is seen to be maximum around the time of solar maximum, lowest during solar minimum, and lower still during the recent protracted solar minimum 2006-2009. One explanation of this behavior can be found in the theory of Schwadron et al. (2010) that argues magnetic flux is injected into interplanetary space by coronal mass ejection eruptions and removed by reconnection in the low solar atmosphere. This produces an HMF intensity that is correlated with sunspot number, and the rapid injection of flux followed by the slow removal by reconnection results in a hysteresis effect that is readily evident in the observations. Here for the first time we apply this theory to the sunspot record going back to 1749 and compare favorably our predictions to the results derived from 10 Be observations. We also make a prediction for the coming solar minimum based on results from the Dalton Minimum.
Recent solar conditions include a prolonged solar minimum (2005–2009) and a solar maximum that has not fully recovered in terms of the Heliospheric Magnetic Field (HMF) strength when compared to the previous maximum values. These anomalies may indicate that we are entering an era of lower solar activity than observed at other times during the space age. We study past solar grand minima, especially the Maunder period (1645–1715) to gain further insight into grand minima. We find the timescale parameters associated with three processes attributed to the magnetic flux balance in the heliosphere using chi-square analysis. We use HMF time series reconstructed based on geomagnetic data and near-Earth spacecraft measurements (OMNI) data to find the fundamental timescales that influence heliospheric field evolution through conversion or opening of magnetic flux from coronal mass ejections (CMEs) into the ambient heliospheric field, removal or loss of the ambient heliospheric field through magnetic reconnection, and interchange reconnection between CME magnetic flux and ambient heliospheric magnetic flux. We also investigate the existence of a floor in the heliospheric magnetic flux, in the absence of CMEs, and show that a floor nT is sufficient to successfully describe the HMF evolution. The minimum value for the HMF at 1 au in the model-predicted historic record is 3.13 ± 0.35 nT. Our model results favorably reproduce paleocosmic data and near-Earth spacecraft measurements data and show how the HMF may evolve through periods of extremely low activity.
Recent papers have linked the heliospheric magnetic flux to the sunspot cycle with good correlation observed between prediction and observation. Other papers have shown a strong correlation between magnetic flux and solar wind proton flux from coronal holes. We combine these efforts with an expectation that the sunspot activity of the approaching solar minimum will resemble the Dalton or Gleissberg Minimum and predict that the magnetic flux and solar wind proton flux over the coming decade will be lower than at any time during the space age. Using these predictions and established theory, we also predict record high galactic cosmic ray intensities over the same years. The analysis shown here is a prediction of global space climate change within which space weather operates. It predicts a new parameter regime for the transient space weather behavior that can be expected during the coming decade.
The Solar Probe Plus mission now under construction will provide the first in situ measurements from inside the orbit of Mercury. The most critical part of that mission will be measurements from inside the Alfvén radius where the Alfvén speed exceeds the wind speed and the physics of the solar wind changes fundamentally due, in part, to the multidirectionality of wave propagation. In this region waves from both sunward and antisunward of the observation point can effect the local dynamics including the turbulent evolution, heating, and acceleration of the plasma. While the location of this point can change with solar wind conditions, we ask the question of whether there is a systematic dependence on the solar cycle that moves the average Alfvén radius to different locations depending upon solar activity. We show that the average Alfvén radius is correlated with the sunspot number and moves systematically from ∼ 15 at solar minimum to 30 RS at solar maximum. The analysis shown here does not predict movement of the Alfvén radius during the recent protracted solar minimum. We project the average Alfvén radius backward and forward in time using the monthly sunspot record to attempt a better understanding of the historical record and predict the behavior of this point during the coming solar cycle.
(2014), Coronal electron temperature in the protracted solar minimum, the cycle 24 mini maximum, and over centuries, J. Geophys. Res. Space Physics, 119, 1486-1492, doi:10.1002 We extend previous analyses to study the evolution of the coronal electron temperature through the protracted solar minimum and observe not only the reduction in coronal temperature in the cycles 23-24 solar minimum but also a small increase in coronal temperature associated with increasing activity during the "mini maximum" in cycle 24. We use a new model of the interplanetary magnetic flux since 1749 to estimate coronal electron temperatures over more than two centuries. The reduction in coronal electron temperature in the cycles 23-24 protracted solar minimum is similar to reductions observed at the beginning of the Dalton Minimum (∼1805-1840). If these trends continue to reflect the evolution of the Dalton Minimum, we will observe further reductions in coronal temperature in the cycles 24-25 solar minimum. Preliminary indications in 2013 do suggest a further post cycle 23 decline in solar activity. Thus, we extend our understanding of coronal electron temperature using the solar wind scaling law and compare recent reductions in coronal electron temperature in the protracted solar minimum to conditions that prevailed in the Dalton Minimum.
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