scholarly journals IMF control of cusp proton emission intensity and dayside convection: implications for component and anti-parallel reconnection

2003 ◽  
Vol 21 (4) ◽  
pp. 955-982 ◽  
Author(s):  
M. Lockwood ◽  
B. S. Lanchester ◽  
H. U. Frey ◽  
K. Throp ◽  
S. K. Morley ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Wind Plasma ◽  
High Time Resolution ◽  
Proton Emission ◽  
Dayside Magnetopause ◽  
Propagation Delays ◽  
Wind Spacecraft ◽  
Upstream Solar Wind ◽  
The Relationship ◽  
The Imf

Abstract. We study a brightening of the Lyman-a emission in the cusp which occurred in response to a short-lived south-ward turning of the interplanetary magnetic field (IMF) during a period of strongly enhanced solar wind plasma concentration. The cusp proton emission is detected using the SI-12 channel of the FUV imager on the IMAGE spacecraft. Analysis of the IMF observations recorded by the ACE and Wind spacecraft reveals that the assumption of a constant propagation lag from the upstream spacecraft to the Earth is not adequate for these high time-resolution studies. The variations of the southward IMF component observed by ACE and Wind allow for the calculation of the ACE-to-Earth lag as a function of time. Application of the derived propagation delays reveals that the intensity of the cusp emission varied systematically with the IMF clock angle, the relationship being particularly striking when the intensity is normalised to allow for the variation in the upstream solar wind proton concentration. The latitude of the cusp migrated equatorward while the lagged IMF pointed southward, confirming the lag calculation and indicating ongoing magnetopause reconnection. Dayside convection, as monitored by the SuperDARN network of radars, responded rapidly to the IMF changes but lagged behind the cusp proton emission response: this is shown to be as predicted by the model of flow excitation by Cowley and Lockwood (1992). We use the numerical cusp ion precipitation model of Lockwood and Davis (1996), along with modelled Lyman-a emission efficiency and the SI-12 instrument response, to investigate the effect of the sheath field clock angle on the acceleration of ions on crossing the dayside magnetopause. This modelling reveals that the emission commences on each reconnected field line 2–2.5 min after it is opened and peaks 3–5 min after it is opened. We discuss how comparison of the Lyman-a intensities with oxygen emissions observed simultaneously by the SI-13 channel of the FUV instrument offers an opportunity to test whether or not the clock angle dependence is consistent with the "component" or the "anti-parallel" reconnection hypothesis.Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; solar wind-magnetosphere interactions) – Space plasma physics (magnetic reconnection)

scholarly journals Impact of solar wind depression on the dayside magnetosphere under northward interplanetary magnetic field

2011 ◽  
Vol 29 (1) ◽  
pp. 31-46 ◽  
Author(s):  
S. Baraka ◽  
L. Ben-Jaffel
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Cell Model ◽  
Dynamic Pressure ◽  
Outer Boundary ◽  
Solar Wind Plasma ◽  
Tail Region ◽  
Dayside Magnetopause

Abstract. We present a follow up study of the sensitivity of the Earth's magnetosphere to solar wind activity using a particles-in-cell model (Baraka and Ben Jaffel, 2007), but here during northward Interplanetary Magnetic Field (IMF). The formation of the magnetospheric cavity and its elongation around the planet is obtained with the classical structure of a magnetosphere with parallel lobes. An impulsive disturbance is then applied to the system by changing the bulk velocity of the solar wind to simulate a decrease in the solar wind dynamic pressure followed by its recovery. In response to the imposed drop in the solar wind velocity, a gap (abrupt depression) in the incoming solar wind plasma appears moving toward the Earth. The gap's size is a ~15 RE and is comparable to the sizes previously obtained for both Bz<0 and Bz=0. During the initial phase of the disturbance along the x-axis, the dayside magnetopause (MP) expands slower than the previous cases of IMF orientations as a result of the abrupt depression. The size of the MP expands nonlinearly due to strengthening of its outer boundary by the northward IMF. Also, during the initial 100 Δt, the MP shrank down from 13.3 RE to ~9.2 RE before it started expanding, a phenomenon that was also observed for southern IMF conditions but not during the no IMF case. As soon as they felt the solar wind depression, cusps widened at high altitude while dragged in an upright position. For the field's topology, the reconnection between magnetospheric and magnetosheath fields is clearly observed in both the northward and southward cusps areas. Also, the tail region in the northward IMF condition is more confined, in contrast to the fishtail-shape obtained in the southward IMF case. An X-point is formed in the tail at ~110 RE compared to ~103 RE and ~80 RE for Bz=0 and Bz<0, respectively. Our findings are consistent with existing reports from many space observatories (Cluster, Geotail, Themis, etc.) for which predictions are proposed to test furthermore our simulation technique.

Solar wind proton precipitation to the surface of Mercury

2020 ◽  
Author(s):  
Shahab Fatemi ◽  
Andrew R. Poppe ◽  
Stas Barabash
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Plasma ◽  
Solar Wind Dynamic Pressure ◽  
Solar Wind Proton ◽  
Entire Surface ◽  
The North ◽  
Proton Precipitation ◽  
Neutral Sodium ◽  
The Imf

&lt;p&gt;We examine the effects of the interplanetary magnetic field (IMF) orientation and solar wind dynamic pressure on the solar wind proton precipitation to the surface of Mercury. We use the Amitis model, a three-dimensional GPU-based hybrid model of plasma (particle ions and fluid electrons), and explain a method we found necessary to accurately calculate plasma precipitation to the surface of Mercury through the highly dynamic Hermean magnetosphere. We use our model to explain ground-based telescope observations of Mercury's neutral sodium exosphere, and compare our simulation results with MESSENGER observations. For the typical solar wind dynamic pressure near the orbit of Mercury (i.e., ~7-8 nPa) our model shows a high solar wind proton flux precipitates through the magnetospheric cusps to the high latitudes on both hemispheres on the dayside with a higher precipitation rate to the southern hemisphere compared to the north, which is associated with the northward displacement of Mercury's intrinsic magnetic dipole. We show that this two peak pattern, which is also a common feature observed for neutral sodium exosphere, is controlled by the radial component (B&lt;sub&gt;x&lt;/sub&gt;) of the IMF and not the B&lt;sub&gt;z&lt;/sub&gt; component. Our model also suggests that the southward IMF and its associated magnetic reconnection do not play a major role in controlling plasma precipitation to the surface of Mercury through the magnetospheric cusps, in agreement with MESSENGER observations that show that, unlike the Earth, there is almost no dependence between the IMF angle and magnetic reconnection rate at Mercury. For the typical solar wind dynamic pressure, our model suggests that the solar wind proton precipitation through the cusps is longitudinally centered near noon with ~11&lt;sup&gt;o&lt;/sup&gt; latitudinal extent in the north and ~21&lt;sup&gt;o&lt;/sup&gt; latitudinal extent in the south, which is consistent with MESSENGER observations. We found an anti-correlation in the incidence area on the surface and the incidence particle rate between the northern and southern cusp precipitation such that the total area and the total rate through both of the cusps remain constant and independent of the IMF orientation. We also show that the solar wind proton incidence rate to the entire surface of Mercury is higher when the IMF has a northward component and nearly half of the incidence flux impacts the low latitudes on the nightside. During extreme solar events (e.g., Coronal Mass Ejections) a large area on the dayside surface of Mercury is exposed to the solar wind plasma, especially in the southern hemisphere. Our model suggests that over 70 nPa solar wind dynamic pressure is required for the entire surface of Mercury to be exposed to the solar wind plasma.&lt;/p&gt;

scholarly journals Are there current-sheet-like structures in the Earth's magnetotail as in the solar wind – results and implications from high time resolution magnetic field measurements by Cluster

2008 ◽  
Vol 26 (7) ◽  
pp. 1889-1895 ◽  
Author(s):  
G. Li ◽  
E. Lee ◽  
G. Parks
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Current Sheet ◽  
Time Resolution ◽  
Field Measurements ◽  
Solar Wind Plasma ◽  
High Time ◽  
High Time Resolution ◽  
Mhd Turbulence ◽  
Flux Tubes

Abstract. Recent studies of solar wind MHD turbulence show that current-sheet-like structures are common in the solar wind and they are a significant source of solar wind MHD turbulence intermittency. While numerical simulations have suggested that such structures can arise from non-linear interactions of MHD turbulence, a recent study by Borovsky (2006), upon analyzing one year worth of ACE data, suggests that these structures may represent the magnetic walls of flux tubes that separate solar wind plasma into distinct bundles and these flux tubes are relic structures originating from boundaries of supergranules on the surface of the Sun. In this work, we examine whether there are such structures in the Earth's magnetotail, an environment vastly different from the solar wind. We use high time resolution magnetic field data of the FGM instrument onboard Cluster C1 spacecraft. The orbits of Cluster traverse through both the solar wind and the Earth's magnetosheath and magnetotail. This makes its dataset ideal for studying differences between solar wind MHD turbulence and that inside the Earth's magnetosphere. For comparison, we also perform the same analysis when Cluster C1 is in the solar wind. Using a data analysis procedure first introduced in Li (2007, 2008), we find that current-sheet-like structures can be clearly identified in the solar wind. However, similar structures do not exist inside the Earth's magnetotail. This result can be naturally explained if these structures have a solar origin as proposed by Borovsky (2006). With such a scenario, current analysis of solar wind MHD turbulence needs to be improved to include the effects due to these curent-sheet-like structures.

scholarly journals Access of solar wind electrons into the Martian magnetosphere

2008 ◽  
Vol 26 (11) ◽  
pp. 3511-3524 ◽  
Author(s):  
E. M. Dubinin ◽  
M. Fraenz ◽  
J. Woch ◽  
E. Roussos ◽  
J. D. Winningham ◽  
...  
Keyword(s):  
Solar Wind ◽  
Vertical Component ◽  
Solar Wind Plasma ◽  
Precipitation Pattern ◽  
Suprathermal Electrons ◽  
Crustal Field ◽  
Additional Protection ◽  
Electron Distributions ◽  
Narrow Bands ◽  
The Imf

Abstract. Electrons with energy of ~40–80 eV measured by the instrument ASPERA-3 on Mars Express and MAG-ER onboard Mars Global Surveyor are used to trace an access of solar wind electrons into the Martian magnetosphere. Crustal magnetic fields create an additional protection from solar wind plasma on the dayside of the Southern Hemisphere by shifting the boundary of the induced magnetosphere (this boundary is often refereed as the magnetic pileup boundary) above strong crustal sources to ~400 km as compared to the Northern Hemisphere. Localized intrusions through cusps are also observed. On the nightside an access into the magnetosphere depends on the IMF orientation. Negative values of the ByIMF component assist the access to the regions with strong crustal magnetizations although electron fluxes are strongly weakened below ~600 km. A precipitation pattern at lower altitudes is formed by intermittent regions with reduced and enhanced electron fluxes. The precipitation sites are longitudinally stretched narrow bands in the regions with a strong vertical component of the crustal field. Fluxes ≥109 cm−2 s−1 of suprathermal electrons necessary to explain the observed aurora emissions are maintained only for the periods with enhanced precipitation. The appearance of another class of electron distributions – inverted V structures, characterized by peaks on energy spectra, is controlled by the IMF. They are clustered in the hemisphere pointed by the interplanetary electric field that implies a constraint on their origin.

scholarly journals Modeling the Lunar Wake Response to a CME Using a Hybrid PIC Model

2022 ◽  
Vol 3 (1) ◽  
pp. 4
Author(s):  
Anthony P. Rasca ◽  
Shahab Fatemi ◽  
William M. Farrell
Keyword(s):  
Solar Wind ◽  
Magnetic Cloud ◽  
Plasma Sheath ◽  
Wake Region ◽  
Plasma Parameters ◽  
Particle In Cell ◽  
Lunar Wake ◽  
Wind Spacecraft ◽  
Upstream Solar Wind ◽  
Mass Ejection

Abstract In the solar wind, a low-density wake region forms downstream of the nightside lunar surface. In this study, we use a series of 3D hybrid particle-in-cell simulations to model the response of the lunar wake to a passing coronal mass ejection (CME). Average plasma parameters are derived from the Wind spacecraft located at 1 au during three distinct phases of a passing halo (Earth-directed) CME on 2015 June 22. Each set of plasma parameters, representing the shock/plasma sheath, a magnetic cloud, and plasma conditions we call the mid-CME phase, are used as the time-static upstream boundary conditions for three separate simulations. These simulation results are then compared with results that use nominal solar wind conditions. Results show a shortened plasma void compared to nominal conditions and a distinctive rarefaction cone originating from the terminator during the CME’s plasma sheath phase, while a highly elongated plasma void reforms during the magnetic cloud and mid-CME phases. Developments of electric and magnetic field intensification are also observed during the plasma sheath phase along the central wake, while electrostatic turbulence dominates along the plasma void boundaries and 2–3 lunar radii R M downstream in the central wake during the magnetic cloud and mid-CME phases. The simulations demonstrate that the lunar wake responds in a dynamic way with the changes in the upstream solar wind during a CME.

scholarly journals Magnetopause energy and mass transfer: results from a global MHD simulation

2006 ◽  
Vol 24 (12) ◽  
pp. 3467-3480 ◽  
Author(s):  
M. Palmroth ◽  
T. V. Laitinen ◽  
T. I. Pulkkinen
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Solar Wind ◽  
Energy Transfer ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Closed Field ◽  
Dayside Magnetopause ◽  
Solar Wind Parameters ◽  
The Imf

Abstract. We use the global MHD model GUMICS-4 to investigate the energy and mass transfer through the magnetopause and towards the closed magnetic field as a response to the interplanetary magnetic field (IMF) clock angle θ=arctan (BY/BZ), IMF magnitude, and solar wind dynamic pressure. We find that the mass and energy transfer at the magnetopause are different both in spatial characteristics and in response to changes in the solar wind parameters. The energy transfer follows best the sin2 (θ/2) dependence, although there is more energy transfer after large energy input, and the reconnection line follows the IMF rotation with a delay. There is no clear clock angle dependence in the net mass transfer through the magnetopause, but the mass transfer through the dayside magnetopause and towards the closed field occurs preferably for northward IMF. The energy transfer occurs through areas at the magnetopause that are perpendicular to the subsolar reconnection line. In contrast, the mass transfer occurs consistently along the reconnection line, both through the magnetopause and towards the closed field. Both the energy and mass transfer are enhanced in response to increased solar wind dynamic pressure, while increasing the IMF magnitude does not affect the transfer quantities as much.

Solar wind temperature anisotropy and its influence on the spectrum of turbulence

2020 ◽  
Author(s):  
Alexander Pitňa ◽  
Jana Šafránkova ◽  
Zdeněk Němeček
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Power Spectra ◽  
Solar Wind Plasma ◽  
Turbulent Medium ◽  
Thermal Velocity ◽  
Temperature Anisotropy ◽  
Ion Density ◽  
Proton Temperature ◽  
Wind Spacecraft

&lt;p&gt;Nearly collisionless solar wind plasma originating in the solar corona is a turbulent medium. The energy within large scale fluctuations is continuously transferred into smaller scales and it eventually reaches scales at which it is converted into a random particle motion, thus heating the plasma. Although the processes that take place within this complex system have been studied for decades, many questions remain unresolved. The power spectra of the fluctuating fields of the magnetic field, bulk velocity, and ion density were studied extensively; however, the spectrum of the thermal velocity is seldom reported and/or discussed. In this paper, we address the difficulty of estimating its power spectrum. We analyze high-cadence (31 ms) thermal velocity measurements of the BMSW instrument onboard the Spektr-R spacecraft and the SWE instrument onboard the Wind spacecraft. We discuss the role of the proton temperature anisotropy (parallel/perpendicular) and its influence on the shape of the power spectra in the inertial range of turbulence.&lt;/p&gt;

Long-term properties of the solar wind and their relation to solar cycles

2020 ◽  
Author(s):  
Anna Salohub ◽  
Jana Šafránkova ◽  
Zdeněk Němeček ◽  
Lubomír Přech ◽  
Tereza Ďurovcová
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Dynamic Pressure ◽  
Solar Wind Speed ◽  
Solar Wind Plasma ◽  
Solar Cycles ◽  
Plasma Parameters ◽  
Wind Spacecraft ◽  
Slow Wind ◽  
Density Dynamic

&lt;p&gt;The solar wind variations during particular solar cycles have been described in many previous studies including the solar cycle 23 that was characterized by a long, deep, and very complex solar minimum with very low values of many solar wind parameters.&lt;/p&gt;&lt;p&gt;Using statistical methods, we analyzed 25 years of Wind spacecraft measurements with motivation to reveal differences and similarities in magnetic field components and solar wind plasma parameters in individual solar cycles. We tracked the changes of the solar magnetic field strength, and components, solar wind speed, density, dynamic pressure, temperature, and composition). Except quiet solar wind conditions during solar minima and maxima, we also selected significant discontinuities (ICME and CIRs) and investigated their influence on profiles of average parameters. For this, we followed other quantities connected with their presence as their average front normals, regions of transitions between high and slow wind streams, special interplanetary magnetic field orientations, etc.). We discuss a behavior of investigated parameters over solar cycles as well as on shorter time scales (in the order of days and hours).&lt;/p&gt;

scholarly journals Average auroral configuration parameterized by geomagnetic activity and solar wind conditions

2010 ◽  
Vol 28 (4) ◽  
pp. 1003-1012 ◽  
Author(s):  
S. E. Milan ◽  
T. A. Evans ◽  
B. Hubert
Keyword(s):  
Solar Wind ◽  
Wind Velocity ◽  
Geomagnetic Activity ◽  
Solar Wind Velocity ◽  
Solar Wind Speed ◽  
Auroral Oval ◽  
Similar Amount ◽  
Solar Wind Parameters ◽  
Upstream Solar Wind ◽  
The Imf

Abstract. Average proton and electron auroral images are compiled from three years of observations by the IMAGE spacecraft, binned according to concurrent KP and upstream solar wind conditions measured by the ACE spacecraft. The solar wind parameters include solar wind velocity, density, and pressure, interplanetary magnetic field (IMF) magnitude and orientation, and an estimate of the magnetopause reconnection rate. We use both (a) the overall variation in brightness in the images and (b) the variation in location of the aurorae with respect to the binning parameters to determine which parameters best order the auroral response. We find that the brightness varies by a factor of ~50 with KP, a similar amount with estimated dayside reconnection voltage, ~15 with the IMF, ~3 with solar wind density, ~2 with solar wind velocity, and ~5 with pressure. Clearly, geomagnetic activity as measured by KP and auroral dynamics are closely associated. In terms of the solar wind-magnetosphere coupling that drives auroral dynamics, the IMF is of paramount importance in modulating this, with solar wind speed and density playing a lesser role. Dayside reconnection voltage, derived from the solar wind velocity and IMF magnitude and orientation, orders the data almost as well as KP, though we find a plateau in the auroral response between voltages of 100 and 150 kV. We also discuss changes in configuration and overall size of the average auroral oval with upstream conditions.

Sign in / Sign up

Export Citation Format

Share Document