scholarly journals Switchback-like structures observed by Solar Orbiter

2021 ◽  
Author(s):  
Andrey Fedorov ◽  
Philippe Louarn ◽  
Christopher Owen ◽  
Lubomir Prech ◽  
Timothy Horbury ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Distribution Function ◽  
Field Data ◽  
Solar Wind Plasma ◽  
Time Interval ◽  
Ion Distribution ◽  
Time Intervals ◽  
Radial Magnetic Field ◽  
Magnetic Field Data

<p>During 27th September 2020 NASA Parker Solar Probe (PSP) and ESA-NASA Solar Orbiter (SolO) have been located around the same Carrington longitude and their latitudinal separation was very small as well. Solar wind plasma and magnetic field data obtained throughout this time interval  allows to consider that sometimes the solar wind, observed by both spacecrafts, originates from the same coronal hole region. Inside these time intervals the SolO radial magnetic field experiences several short variations similar to the "switchbacks" regularly observed by PSP. We used the SolO SWA-PAS proton analyzer data to analyze the ion distribution function variations inside such switchback-like events to understand if such events are really "remains" of the alfvenic structures observed below 60 Rs.</p>

Possible instrumental effects on moments computation of the solar wind proton velocity distribution function: Helios observations

2020 ◽  
Vol 639 ◽  
pp. A82 ◽  
Author(s):  
R. De Marco ◽  
R. Bruno ◽  
R. D’Amicis ◽  
D. Telloni ◽  
D. Perrone
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Distribution Function ◽  
Velocity Distribution ◽  
Field Data ◽  
Velocity Distribution Function ◽  
Instrumental Effects ◽  
Solar Wind Proton ◽  
Magnetic Field Data ◽  
Density Values

The solar wind is a highly turbulent medium in which most of the energy is carried by Alfvénic fluctuations. These fluctuations have a wide range of scales whose high-frequency tail can be relevant for the sampling techniques commonly used to detect the particle distribution in phase space in situ. We analyze the effect of Alfvénic fluctuations on moments computation of the solar wind proton velocity distribution for a plasma sensor, whose sampling time is comparable or even longer than the typical timescale of the velocity fluctuations induced by these perturbations. In particular, we numerically simulated the sampling procedure used on board Helios 2. We directly employed magnetic field data recorded by the Helios 2 magnetometer, when the s/c was immersed in fast wind during its primary mission to the Sun, to simulate Alfvénic fluctuations. More specifically, we used magnetic field data whose cadence of 4 Hz is considerably higher than that the plasma sensor needed to sample a full velocity distribution function, and we average these data to 1 Hz, which is the spin period of Helios. Density values, which are necessary to build Alfvénic fluctuations at these scales, are not available because the cadence of the Helios plasma data is 40.5 s. The adopted solution is based on the assumption that the available Helios plasma density power spectrum can be extended to the same frequencies as the magnetic field spectrum by extrapolating the power-law fit of the low-frequency range to the frequencies relevant for this study. Surrogate density values in the time domain are then obtained by inverse transforming this spectrum. We show that it cannot be excluded that relevant instrumental effects strongly contribute to generate interesting spectral and kinetic features that have been interpreted in the past literature as exclusively due to physical mechanisms.

scholarly journals Predictions of local ground geomagnetic field fluctuations during the 7-10 November 2004 events studied with solar wind driven models

2005 ◽  
Vol 23 (9) ◽  
pp. 3095-3101 ◽  
Author(s):  
P. Wintoft ◽  
M. Wik ◽  
H. Lundstedt ◽  
L. Eliasson
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Flow Direction ◽  
Strong Dependence ◽  
Solar Wind Plasma ◽  
Magnetic Field Data ◽  
Solar Wind Magnetic Field ◽  
Solar Wind Flow ◽  
Field Fluctuations ◽  
Ground Magnetic

Abstract. The 7-10 November 2004 period contains two events for which the local ground magnetic field was severely disturbed and simultaneously, the solar wind displayed several shocks and negative Bz periods. Using empirical models the 10-min RMS and at Brorfelde (BFE, 11.67° E, 55.63° N), Denmark, are predicted. The models are recurrent neural networks with 10-min solar wind plasma and magnetic field data as inputs. The predictions show a good agreement during 7 November, up until around noon on 8 November, after which the predictions become significantly poorer. The correlations between observed and predicted log RMS is 0.77 during 7-8 November but drops to 0.38 during 9-10 November. For RMS the correlations for the two periods are 0.71 and 0.41, respectively. Studying the solar wind data for other L1-spacecraft (WIND and SOHO) it seems that the ACE data have a better agreement to the near-Earth solar wind during the first two days as compared to the last two days. Thus, the accuracy of the predictions depends on the location of the spacecraft and the solar wind flow direction. Another finding, for the events studied here, is that the and models showed a very different dependence on Bz. The model is almost independent of the solar wind magnetic field Bz, except at times when Bz is exceptionally large or when the overall activity is low. On the contrary, the model shows a strong dependence on Bz at all times.

Interplanetary shocks at 5 AU and their effects on Jupiter's decametric radio emissions

2020 ◽  
Author(s):  
Ezequiel Echer
Keyword(s):  
Magnetic Field ◽  
Field Data ◽  
Heliocentric Distance ◽  
Solar Wind Plasma ◽  
Interplanetary Shock ◽  
Interplanetary Shocks ◽  
Magnetic Field Data ◽  
Radio Emissions ◽  
Abrupt Changes

<p>Interplanetary shocks cause large and abrupt changes in solar wind plasma and magnetic field parameters. Shock occurrence and strength are dependent on the heliocentric distance. Further, shocks have important effects on planetary magnetospheres, such as causing large magnetospheric compressions or expansions, and triggering auroral activity emissions. In this work recent results regarding interplanetary shock parameters determined from analysis of in-situ spacecraft plasma and magnetic field data measured near Jupiter’s orbit are presented. The distribution of parameters for both fast forward and fast reverse shocks is analysed and compared with interplanetary shocks detected at other heliocentric distances, Further, an analysis of  interplanetary shock effects on Jupiter decametric auroral radio emissions independent of Io (non-Io DAM) is presented. </p>

scholarly journals Statistical dependence of auroral ionospheric currents on solar wind and geomagnetic parameters from 5 years of CHAMP satellite data

2009 ◽  
Vol 27 (3) ◽  
pp. 1005-1017 ◽  
Author(s):  
L. Juusola ◽  
K. Kauristie ◽  
O. Amm ◽  
P. Ritter
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Data ◽  
Dynamic Pressure ◽  
Auroral Oval ◽  
Solar Wind Dynamic Pressure ◽  
Total Field ◽  
Magnetic Field Data ◽  
Champ Satellite ◽  
Field Aligned Current

Abstract. The effects of the solar wind dynamic pressure (P), the z component of the solar wind magnetic field (Bz), the merging electric field (Em), season and the Kp index on R1 and R2 field-aligned currents are studied statistically using magnetic field data from the CHAMP satellite during 2001–2005. The ionospheric and field-aligned currents are determined from the magnetic field data by the recently developed 1-D Spherical Elementary Current System (SECS) method. During southward IMF, increasing |Bz| is observed to clearly increase the total field-aligned current, while during northward IMF, the amount of field-aligned current remains fairly constant regardless of |Bz|. The dependence of the field-aligned current on Bz is given by |Ir[MA]|=0.054·Bz[nT]2−0.34·Bz[nT]+2.4. With increasing P, the intensity of the field-aligned current is also found to increase according to |Ir[MA]|=0.62·P[nPa]+1.6, and the auroral oval is observed to move equatorward. Increasing Em produces similar behaviour, described by |Ir[MA]|=1.41·Em[mV/m]+1.4. While the absolute intensity of the ionospheric current is stronger during negative than during positive Bz, the relative change in the intensity of the currents produced by a more intense solar wind dynamic pressure is observed to be approximately the same regardless of the Bz direction. Increasing Kp from 0 to ≥5 widens the auroral oval and moves it equatorward from between 66°–74° AACGM latitude to 59°–71° latitude. The total field aligned current as a function of Kp is given by |Ir[MA]|=1.1·Kp+0.6. In agreement with previous studies, total field-aligned current in the summer is found to be 1.4 times stronger than in the winter.

scholarly journals Forecasting intense geomagnetic activity using interplanetary magnetic field data

2008 ◽  
Vol 26 (12) ◽  
pp. 3989-3998 ◽  
Author(s):  
E. Saiz ◽  
C. Cid ◽  
Y. Cerrato
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Field Data ◽  
Solar Wind Plasma ◽  
Magnetic Field Data ◽  
Interplanetary Magnetic Fields ◽  
Physical Mechanisms ◽  
Faraday’S Law ◽  
Forecasting Method ◽  
New Interpretation

Abstract. Southward interplanetary magnetic fields are considered traces of geoeffectiveness since they are a main agent of magnetic reconnection of solar wind and magnetosphere. The first part of this work revises the ability to forecast intense geomagnetic activity using different procedures available in the literature. The study shows that current methods do not succeed in making confident predictions. This fact led us to develop a new forecasting procedure, which provides trustworthy results in predicting large variations of Dst index over a sample of 10 years of observations and is based on the value Bz only. The proposed forecasting method appears as a worthy tool for space weather purposes because it is not affected by the lack of solar wind plasma data, which usually occurs during severe geomagnetic activity. Moreover, the results obtained guide us to provide a new interpretation of the physical mechanisms involved in the interaction between the solar wind and the magnetosphere using Faraday's law.

scholarly journals Observation of magnetic reconnection and current sheets in the solar wind

2009 ◽  
Vol 5 (S264) ◽  
pp. 369-372
Author(s):  
Pablo R. Muñoz ◽  
Abraham C.-L. Chian ◽  
Rodrigo A. Miranda ◽  
Michio Yamada
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
Field Data ◽  
Large Scale ◽  
Physical Characteristics ◽  
Magnetic Field Data ◽  
Current Sheets

AbstractWe apply single- and multi-spacecraft techniques to search for currents sheets in the solar wind during the ICME event of 21 January 2005, using the Cluster magnetic field data. Two large-scale currents sheets are detected at the leading boundary of the ICME ejecta using the single-spacecraft technique, which exhibit physical characteristics typical of magnetic reconnection exhausts in the solar wind.

An Augmented Iteratively Re-weighted and Refined Least Squares Method for lp Minimization Problem in Inverse Modeling of Potential Field Magnetic Data

2020 ◽  
Vol 1 (3) ◽  
Author(s):  
Maysam Abedi
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Least Squares ◽  
Minimization Problem ◽  
Potential Field ◽  
Field Data ◽  
Least Squares Method ◽  
Porphyry Copper ◽  
Magnetic Data ◽  
Magnetic Field Data

The presented work examines application of an Augmented Iteratively Re-weighted and Refined Least Squares method (AIRRLS) to construct a 3D magnetic susceptibility property from potential field magnetic anomalies. This algorithm replaces an lp minimization problem by a sequence of weighted linear systems in which the retrieved magnetic susceptibility model is successively converged to an optimum solution, while the regularization parameter is the stopping iteration numbers. To avoid the natural tendency of causative magnetic sources to concentrate at shallow depth, a prior depth weighting function is incorporated in the original formulation of the objective function. The speed of lp minimization problem is increased by inserting a pre-conditioner conjugate gradient method (PCCG) to solve the central system of equation in cases of large scale magnetic field data. It is assumed that there is no remanent magnetization since this study focuses on inversion of a geological structure with low magnetic susceptibility property. The method is applied on a multi-source noise-corrupted synthetic magnetic field data to demonstrate its suitability for 3D inversion, and then is applied to a real data pertaining to a geologically plausible porphyry copper unit.  The real case study located in  Semnan province of  Iran  consists  of  an arc-shaped  porphyry  andesite  covered  by  sedimentary  units  which  may  have  potential  of  mineral  occurrences, especially  porphyry copper. It is demonstrated that such structure extends down at depth, and consequently exploratory drilling is highly recommended for acquiring more pieces of information about its potential for ore-bearing mineralization.

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