The proton temperature and the total hourly variance of the magnetic field components in different solar wind speed regions

Solar Physics ◽  
1989 ◽  
Vol 119 (1) ◽  
pp. 197-206 ◽  
Author(s):  
Chuan-Yi Tu ◽  
John W. Freeman ◽  
R. E. Lopez
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Wind Speed ◽  
Solar Wind Speed ◽  
Proton Temperature ◽  
The Magnetic Field

scholarly journals Cluster observations of sudden impulses in the magnetotail caused by interplanetary shocks and pressure increases

2005 ◽  
Vol 23 (2) ◽  
pp. 609-624 ◽  
Author(s):  
K. E. J. Huttunen ◽  
J. Slavin ◽  
M. Collier ◽  
H. E. J. Koskinen ◽  
A. Szabo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Speed ◽  
Interplanetary Shock ◽  
Wind Pressure ◽  
Shock Propagation ◽  
Interplanetary Shocks ◽  
Maximum Variance ◽  
The Magnetic Field

Abstract. Sudden impulses (SI) in the tail lobe magnetic field associated with solar wind pressure enhancements are investigated using measurements from Cluster. The magnetic field components during the SIs change in a manner consistent with the assumption that an antisunward moving lateral pressure enhancement compresses the magnetotail axisymmetrically. We found that the maximum variance SI unit vectors were nearly aligned with the associated interplanetary shock normals. For two of the tail lobe SI events during which Cluster was located close to the tail boundary, Cluster observed the inward moving magnetopause. During both events, the spacecraft location changed from the lobe to the magnetospheric boundary layer. During the event on 6 November 2001 the magnetopause was compressed past Cluster. We applied the 2-D Cartesian model developed by collier98 in which a vacuum uniform tail lobe magnetic field is compressed by a step-like pressure increase. The model underestimates the compression of the magnetic field, but it fits the magnetic field maximum variance component well. For events for which we could determine the shock normal orientation, the differences between the observed and calculated shock propagation times from the location of WIND/Geotail to the location of Cluster were small. The propagation speeds of the SIs between the Cluster spacecraft were comparable to the solar wind speed. Our results suggest that the observed tail lobe SIs are due to lateral increases in solar wind dynamic pressure outside the magnetotail boundary.

scholarly journals The relativistic electron response in the outer radiation belt during magnetic storms

2002 ◽  
Vol 20 (7) ◽  
pp. 957-965 ◽  
Author(s):  
R. H. A. Iles ◽  
A. N. Fazakerley ◽  
A. D. Johnstone ◽  
N. P. Meredith ◽  
P. Bühler
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Wind Speed ◽  
Interplanetary Magnetic Field ◽  
Relativistic Electron ◽  
Radiation Belt ◽  
Solar Wind Speed ◽  
Recovery Phase ◽  
Magnetic Storms ◽  
Outer Radiation Belt

Abstract. The relativistic electron response in the outer radiation belt during magnetic storms has been studied in relation to solar wind and geomagnetic parameters during the first six months of 1995, a period in which there were a number of recurrent fast solar wind streams. The relativistic electron population was measured by instruments on board the two microsatellites, STRV-1a and STRV-1b, which traversed the radiation belt four times per day from L ~ 1 out to L ~ 7 on highly elliptical, near-equatorial orbits. Variations in the E > 750 keV and E > 1 MeV electrons during the main phase and recovery phase of 17 magnetic storms have been compared with the solar wind speed, interplanetary magnetic field z-component, Bz , the solar wind dynamic pressure and Dst *. Three different types of electron responses are identified, with outcomes that strongly depend on the solar wind speed and interplanetary magnetic field orientation during the magnetic storm recovery phase. Observations also confirm that the L-shell, at which the peak enhancement in the electron count rate occurs has a dependence on Dst *.Key words. Magnetospheric physics (energetic particles, trapped; storms and substorms) – Space plasma physics (charged particle motion and accelerations)

scholarly journals Peculiar Current Solar-Minimum Structure of the Heliosphere

2009 ◽  
Vol 5 (H15) ◽  
pp. 484-487
Author(s):  
P. K. Manoharan
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Solar Minimum ◽  
Large Scale ◽  
Solar Wind Speed ◽  
Heliospheric Current Sheet ◽  
Coronal Density ◽  
Current Minimum ◽  
Similar Phase ◽  
The Magnetic Field

AbstractIn this paper, I review the results of 3-D evolution of the inner heliosphere over the solar cycle 23, based on observations of interplanetary scintillation (IPS) made at 327 MHz using the Ooty Radio Telescope. The large-scale features of solar wind speed and density turbulence of the current minimum are remarkably different from that of the previous cycle. The results on the solar wind density turbulence show that (1) the current solar minimum is experiencing a low level of coronal density turbulence, to a present value of ~50% lower than the previous similar phase, and (2) the scattering diameter of the corona has decreased steadily after the year 2003. The results on solar wind speed are consistent with the magnetic field strength at the poles and the warping of heliospheric current sheet.

scholarly journals Effect of the solar wind conditions on the ionospheric equivalent current systems

2013 ◽  
Vol 31 (3) ◽  
pp. 489-501 ◽  
Author(s):  
J. J. Zhang ◽  
C. Wang ◽  
B. B. Tang ◽  
H. Li
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Wind Speed ◽  
Current System ◽  
Solar Wind Speed ◽  
Lower Latitude ◽  
Equivalent Current ◽  
Mhd Model ◽  
Current Systems ◽  
The Imf

Abstract. We employ a global magnetohydrodynamics (MHD) model, namely the PPMLR-MHD model, to investigate the effect of the solar wind conditions, such as the interplanetary magnetic field (IMF) clock angle, southward IMF magnitude and solar wind speed, on the average pattern of the ionospheric equivalent current systems (ECS). A new method to derive ECS from the MHD model is proposed and applied, which takes account of the oblique magnetic field line effects. The model results indicate that when the IMF is due northward, the ECS are very weak while the current over polar region is stronger than the lower latitude; when the IMF rotates southward, the two-cell current system dominates, the eastward electrojet on the afternoon sector and the westward electrojet on the dawn sector increase rapidly while the westward electrojet is stronger than the eastward electrojet. Under southward IMF, the intensity of the westward electrojet and eastward electrojet both increase with the increase of the southward IMF magnitude and solar wind speed, and the increase is very sharp for the westward electrojet. Furthermore, we compare the geomagnetic perturbations on the ground represented by the simulated average ECS with the observation-based statistical results under similar solar wind conditions. It is found that the model results generally match with the observations, but the underestimation of the eastward equivalent current on the dusk sector is the main limitation of the present model.

scholarly journals Evidence for Plasma Heating at Thin Current Sheets in the Solar Wind

2022 ◽  
Vol 924 (2) ◽  
pp. L22
Author(s):  
Zilu Zhou ◽  
Xiaojun Xu ◽  
Pingbing Zuo ◽  
Yi Wang ◽  
Qi Xu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Plasma Heating ◽  
Magnetic Field Direction ◽  
Current Sheets ◽  
Proton Temperature ◽  
Fast Wind ◽  
Wind Spacecraft ◽  
Slow Wind ◽  
The Magnetic Field

Abstract Plasma heating at thin current sheets in the solar wind is examined using magnetic field and plasma data obtained by the WIND spacecraft in the past 17 years from 2004 to 2019. In this study, a thin current sheet is defined by an abrupt rotation (larger than 45°) of the magnetic field direction in 3 s. A total of 57,814 current sheets have been identified, among which 25,018 current sheets are located in the slow wind and 19,842 current sheets are located in the fast wind. Significant plasma heating is found at current sheets in both slow and fast wind. Proton temperature increases more significantly at current sheets in the fast wind than in the slow wind, while the enhancement in electron temperature is less remarkable at current sheets in the fast wind. The results reveal that plasma heating commonly exists at thin current sheets in the solar wind regardless of the wind speed, but the underlying heating mechanisms might be different.

Solar cycle variations in differential instrumental responses from ground‑based geomagnetic records

2020 ◽  
Author(s):  
Stuart Gilder ◽  
Michael Wack ◽  
Elena Kronberg ◽  
Ameya Prabhu
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Cycle ◽  
High Speed ◽  
Magnetic Measurements ◽  
Solar Wind Speed ◽  
Maximum Amplitude ◽  
Auroral Oval ◽  
Wide Frequency Range ◽  
The Magnetic Field

<p>We developed a new technique based on differences in instrument responses from ground-based magnetic measurements that extracts the frequency content of the magnetic field with periods ranging from 0.1 to 100 seconds. By stacking hourly averages over an entire year, we found that the maximum amplitude of the magnetic field oscillations occurred near solar noon over diurnal periods at all latitudes except in the auroral oval. Seasonal variability was identified only at high latitude. Long-term trends in field oscillations followed the solar cycle, yet the maxima occurred during the declining phase when high-speed streams in the solar wind dominated. A parameter based on solar wind speed and the relative variability of the interplanetary magnetic field correlated robustly with the ground-based measurements. Our findings suggest that turbulence in the solar wind, its interaction at the magnetopause, and its propagation into the magnetosphere stimulate magnetic field fluctuations at the ground on the dayside over a wide frequency range. Our method enables the study of field line oscillations using the publicly available, worldwide database of geomagnetic observatories.</p>

scholarly journals Correlated solar wind speed, density, and magnetic field changes at Voyager 2

2003 ◽  
Vol 30 (23) ◽  
pp. n/a-n/a ◽  
Author(s):  
J. D. Richardson ◽  
C. Wang ◽  
L. F. Burlaga
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Wind Speed ◽  
Solar Wind Speed ◽  
Voyager 2
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