scholarly journals The Role of Solar Wind Density in Cross Polar Cap Potential Saturation Under Northward Interplanetary Magnetic Field

2017 ◽  
Vol 44 (23) ◽  
pp. 11,729-11,734 ◽  
Author(s):  
Dong Lin ◽  
Binzheng Zhang ◽  
Wayne A. Scales ◽  
Michael Wiltberger ◽  
C. Robert Clauer ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Solar Wind Density ◽  
Polar Cap ◽  
Cross Polar Cap Potential

scholarly journals A new formulation for the ionospheric cross polar cap potential including saturation effects

2005 ◽  
Vol 23 (11) ◽  
pp. 3533-3547 ◽  
Author(s):  
A. J. Ridley
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Mach Number ◽  
Interplanetary Magnetic Field ◽  
Polar Cap ◽  
Pressure Balance ◽  
Simple Modification ◽  
Post Shock ◽  
Cross Polar Cap Potential ◽  
New Formulation

Abstract. It is known that the ionospheric cross polar cap potential (CPCP) saturates when the interplanetary magnetic field (IMF) Bz becomes very large. Few studies have offered physical explanations as to why the polar cap potential saturates. We present 13 events in which the reconnection electric field (REF) goes above 12mV/m at some time. When these events are examined as typically done in previous studies, all of them show some signs of saturation (i.e., over-prediction of the CPCP based on a linear relationship between the IMF and the CPCP). We show that by taking into account the size of the magnetosphere and the fact that the post-shock magnetic field strength is strongly dependent upon the solar wind Mach number, we can better specify the ionospheric CPCP. The CPCP (Φ) can be expressed as Φ=(10-4v2+11.7B(1-e-Ma/3)sin3(θ/2)) {rms/9 (where v is the solar wind velocity, B is the combined Y and Z components of the interplanetary magnetic field, Ma is the solar wind Mach number, θ=acos(Bz/B), and rms is the stand-off distance to the magnetopause, assuming pressure-balance between the solar wind and the magnetosphere). This is a simple modification of the original Boyle et al. (1997) formulation.

scholarly journals On the relaxation of magnetospheric convection when <I>B</I><sub>z</sub> turns northward

2012 ◽  
Vol 30 (6) ◽  
pp. 927-928 ◽  
Author(s):  
M. C. Kelley
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Fields ◽  
Interplanetary Magnetic Field ◽  
Time Constant ◽  
Joule Heat ◽  
Upper Atmosphere ◽  
Joule Dissipation ◽  
Polar Cap ◽  
Magnetospheric Convection

Abstract. The solar wind inputs considerable energy into the upper atmosphere, particularly when the interplanetary magnetic field (IMF) is southward. According to Poynting's theorem (Kelley, 2009), this energy becomes stored as magnetic fields and then is dissipated by Joule heat and by energizing the plasmasheet plasma. If the IMF turns suddenly northward, very little energy is transferred into the system while Joule dissipation continues. In this process, the polar cap potential (PCP) decreases. Experimentally, it was shown many years ago that the energy stored in the magnetosphere begins to decay with a time constant of two hours. Here we use Poynting's theorem to calculate this time constant and find a result that is consistent with the data.

scholarly journals Saturation of the magnetosphere during superstorms: new results from magnetogram inversion technique

2017 ◽  
Vol 3 (3) ◽  
pp. 15-19
Author(s):  
Владимир Мишин ◽  
Vladimir Mishin ◽  
Юрий Караваев ◽  
Yuriy Karavaev
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Flux ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Field ◽  
Dynamic Pressure ◽  
Magnetic Clouds ◽  
Polar Cap ◽  
Thermal Pressure ◽  
Dayside Magnetopause

From data of three three superstorms we study new features of the saturation process of the polar cap magnetic flux deceleration of its area at strengthening the solar wind (SW). It is shown that the saturation of the polar cap is observed at growth of the SW dynamic pressure and vertical IMF component for both signs. Saturation is realized not only during the passage of interplanetary magnetic clouds, but also at significant enhancement of SW density, when the SW thermal pressure is comparable with the pressure of the interplanetary magnetic field. We assume that at such condiitions the saturation is caused not only by a decrease in the efficiency of reconnection at the dayside magnetopause, but mainly by a finite magnetosphere compressibility –stopping the magnetopause compression due to the rapid Eathward growth of the geomagnetic field, ie, interior magnetospheric structure of the geomagnetic field

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