IMF BX and Dipole Tilt Dependence on Transpolar Arcs

2021 ◽  
Author(s):  
Simon Thor ◽  
Anita Kullen ◽  
Lei Cai
Keyword(s):  
Solar Wind ◽  
Observational Data ◽  
Strong Correlation ◽  
Auroral Oval ◽  
Clear Correlation ◽  
Satellite Measurements ◽  
Observational Bias ◽  
Wind Distribution ◽  
Dipole Tilt

<p>Transpolar arcs (TPAs) are predicted by many models to appear in both hemispheres, as so-called conjugate TPAs. However, some observations have suggested that this is not always the case, and that there is an IMF B<sub>x</sub> dependence on whether TPAs appear on both hemispheres or not. Specifically, it has been suggested that TPAs only appear on the northern hemisphere for negative IMF B<sub>X</sub> and vice versa for positive IMF B<sub>X</sub>. Furthermore, a positive Earth dipole tilt is predicted to have a similar effect on TPA occurrences as a negative IMF B<sub>X</sub> and vice versa. It is also known that TPAs appear on different locations on the auroral oval, i.e., dawn-, dusk- or both sides of the oval, depending on IMF B<sub>Y</sub>. However, the role of IMF B<sub>X</sub> and IMF B<sub>Z</sub> for the TPA location remains unclear, with some previous observations suggesting a correlation with IMF B<sub>X</sub>.</p><p>In this study, we investigate the influence of IMF B<sub>X</sub> and dipole tilt on TPAs by statistically analyzing observational data. We analyze TPA datasets from four previous studies, as well as our own TPA dataset, created from DMSP satellite measurements. At first glance, the data suggests that there is a strong correlation between both IMF B<sub>X</sub> and dipole tilt, and TPA observations in a specific hemisphere. However, when normalizing the data to the solar wind distribution and when taking observational bias into account, this correlation disappears. We therefore conclude that there is no clear correlation between neither IMF B<sub>X</sub> nor dipole tilt and in which hemisphere a TPA appears. We further analyze four of the five datasets with respect to dawn-dusk appearances of TPAs and its correlation to IMF B<sub>X</sub>, B<sub>Y</sub> and B<sub>Z</sub>. Here, the results for the datasets mostly agree with previous observations. Finally, we discuss the potential causes for the few non-conjugate TPAs, by studying our own TPA dataset in further detail.</p>

scholarly journals Ground-based and satellite observations of high-latitude auroral activity in the dusk sector of the auroral oval

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1683-1696 ◽  
Author(s):  
K. Kauristie ◽  
T. I. Pulkkinen ◽  
O. Amm ◽  
A. Viljanen ◽  
M. Syrjäsuo ◽  
...  
Keyword(s):  
Solar Wind ◽  
High Latitude ◽  
Auroral Oval ◽  
Outer Edge ◽  
Satellite Observations ◽  
Mhd Waves ◽  
Clear Correlation ◽  
Close Relationship ◽  
Magnetic Pulsations ◽  
Dusk Sector

Abstract. On 7 December 2000, during 13:30–15:30 UT the MIRACLE all-sky camera at Ny Ålesund observed auroras at high-latitudes (MLAT ~ 76) simultaneously when the Cluster spacecraft were skimming the magnetopause in the same MLT sector (at ~ 16:00–18:00 MLT). The location of the auroras (near the ionospheric convection reversal boundary) and the clear correlation between their dynamics and IMF variations suggests their close relationship with R1 currents. Consequently, we can assume that the Cluster spacecraft were making observations in the magnetospheric region associated with the auroras, although exact magnetic conjugacy between the ground-based and satellite observations did not exist. The solar wind variations appeared to control both the behaviour of the auroras and the magnetopause dynamics. Auroral structures were observed at Ny Ålesund especially during periods of negative IMF BZ. In addition, the Cluster spacecraft experienced periodic (T ~ 4 - 6 min) encounters between magnetospheric and magnetosheath plasmas. These undulations of the boundary can be interpreted as a consequence of tailward propagating magnetopause surface waves. Simultaneous dusk sector ground-based observations show weak, but discernible magnetic pulsations (Pc 5) and occasionally periodic variations (T ~ 2 - 3 min) in the high-latitude auroras. In the dusk sector, Pc 5 activity was stronger and had characteristics that were consistent with a field line resonance type of activity. When IMF BZ stayed positive for a longer period, the auroras were dimmer and the spacecraft stayed at the outer edge of the magnetopause where they observed electromagnetic pulsations with T ~ 1 min. We find these observations interesting especially from the viewpoint of previously presented studies relating poleward-moving high-latitude auroras with pulsation activity and MHD waves propagating at the magnetospheric boundary layers.Key words. Ionosphere (ionosphere-magnetosphere interaction) – Magnetospheric physics (auroral phenomena; solar wind – magnetosphere interactions)

Quantifying sources and sinks of trace gases using space-borne measurements: current and future science

2008 ◽  
Vol 366 (1885) ◽  
pp. 4509-4528 ◽  
Author(s):  
Paul I Palmer
Keyword(s):  
Trace Gases ◽  
Lower Troposphere ◽  
Biological Interactions ◽  
Satellite Measurements ◽  
Sources And Sinks ◽  
The Past ◽  
Fundamental Understanding ◽  
Earth’S Climate ◽  
New Generation

We have been observing the Earth's upper atmosphere from space for several decades, but only over the past decade has the necessary technology begun to match our desire to observe surface air pollutants and climate-relevant trace gases in the lower troposphere, where we live and breathe. A new generation of Earth-observing satellites, capable of probing the lower troposphere, are already orbiting hundreds of kilometres above the Earth's surface with several more ready for launch or in the planning stages. Consequently, this is one of the most exciting times for the Earth system scientists who study the countless current-day physical, chemical and biological interactions between the Earth's land, ocean and atmosphere. First, I briefly review the theory behind measuring the atmosphere from space, and how these data can be used to infer surface sources and sinks of trace gases. I then present some of the science highlights associated with these data and how they can be used to improve fundamental understanding of the Earth's climate system. I conclude the paper by discussing the future role of satellite measurements of tropospheric trace gases in mitigating surface air pollution and carbon trading.

scholarly journals Cusp-like plasma in high altitudes: a statistical study of the width and location of the cusp from Magion-4

2002 ◽  
Vol 20 (3) ◽  
pp. 311-320 ◽  
Author(s):  
J. Mĕrka ◽  
J. Šafránková ◽  
Z. Nĕmeček
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
High Altitudes ◽  
Data Set ◽  
Latitudinal Dependence ◽  
Merging Process ◽  
Low Altitude ◽  
Field Lines ◽  
The Magnetic Field ◽  
Dipole Tilt

Abstract. The width of the cusp region is an indicator of the strength of the merging process and the degree of opening of the magnetosphere. During three years, the Magion-4 satellite, as part of the Interball project, has collected a unique data set of cusp-like plasma observations in middle and high altitudes. For a comparison of high- and low-altitude cusp determination, we map our observations of cusp-like plasma along the magnetic field lines down to the Earth’s surface. We use the Tsyganenko and Stern 1996 model of the magnetospheric magnetic field for the mapping, taking actual solar wind and IMF parameters from the Wind observations. The footprint positions show substantial latitudinal dependence on the dipole tilt angle. We fit this dependence with a linear function and subtract this function from observed cusp position. This process allows us to study both statistical width and location of the inspected region as a function of the solar wind and IMF parameters. Our processing of the Magion-4 measurements shows that high-altitude regions occupied by the cusp-like plasma (cusp and cleft) are projected onto a much broader area (in magnetic local time as well as in a latitude) than that determined in low altitudes. The trends of the shift of the cusp position with changes in the IMF direction established by low-altitude observations have been confirmed.Key words. Magnetospheric physics (magnetopause, cusp and boundary layer; solar wind – magnetosphere interactions)

scholarly journals Remotely distinguishing and mapping endogenic water on the Moon

2017 ◽  
Vol 375 (2094) ◽  
pp. 20150391 ◽  
Author(s):  
Rachel L. Klima ◽  
Noah E. Petro
Keyword(s):  
Solar Wind ◽  
Spatial Distribution ◽  
Solar System ◽  
The Moon ◽  
Testing Hypotheses ◽  
Origin And Evolution ◽  
Lunar Interior ◽  
Geological Features ◽  
Insight Into

Water and/or hydroxyl detected remotely on the lunar surface originates from several sources: (i) comets and other exogenous debris; (ii) solar-wind implantation; (iii) the lunar interior. While each of these sources is interesting in its own right, distinguishing among them is critical for testing hypotheses for the origin and evolution of the Moon and our Solar System. Existing spacecraft observations are not of high enough spectral resolution to uniquely characterize the bonding energies of the hydroxyl molecules that have been detected. Nevertheless, the spatial distribution and associations of H, OH − or H 2 O with specific lunar lithologies provide some insight into the origin of lunar hydrous materials. The global distribution of OH − /H 2 O as detected using infrared spectroscopic measurements from orbit is here examined, with particular focus on regional geological features that exhibit OH − /H 2 O absorption band strengths that differ from their immediate surroundings. This article is part of the themed issue ‘The origin, history and role of water in the evolution of the inner Solar System’.

scholarly journals The role of school activities in reducing school dropout phenomenon from the point of view of the principals of public schools in the Deir Ala district in Jordan: دور الأنشطة المدرسية في الحد من ظاهرة التسرب المدرسي من وجهة نظر مديري المدارس الحكومية في لواء دير علا بالأردن

2020 ◽  
Vol 4 (4) ◽  
Author(s):  
Raida Hussein Mohammed Sous
Keyword(s):  
Public Schools ◽  
Strong Correlation ◽  
School Dropout ◽  
Point Of View ◽  
Department Heads ◽  
School Dropouts ◽  
School Activities ◽  
Descriptive Approach ◽  
Educational Field

The study aimed at uncovering the role of school activities in reducing school dropout phenomenon from the point of view of the principals of public schools in the Deir Ala district. The researcher used the descriptive approach. In order to achieve the goal of the study, The results showed that the role of school activities in reducing the phenomenon of school dropout with an average of (3.66). The order of the fields ranked in descending order according to the level of fields: Educational field, reached (3.92) (3.40), all of which are rated (high) That the administrative level of creativity of the department heads are high average (3.94), also showed a strong correlation by (0.82). In the light of the results, a number of recommendations and proposals were presented to raise the level of school activities to reduce school dropouts.

Comparison of polar ionospheric behavior at Arctic and Antarctic regions for improved satellite-based positioning

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Arun Kumar Singh ◽  
Sampad Kumar Panda
Keyword(s):  
Magnetic Field ◽  
Interplanetary Magnetic Field ◽  
Arctic Region ◽  
Auroral Oval ◽  
Ionospheric Scintillation ◽  
Electron Content ◽  
Total Electron ◽  
Polar Latitude ◽  
Tec Variability

Abstract In this paper, we investigate the hemispheric symmetric and asymmetric characteristics of ionospheric total electron content (TEC) and its dependency on the interplanetary magnetic field (IMF) in the northern and southern polar ionosphere. The changes in amplitude and phase scintillation are also probed through Global Ionospheric Scintillation and TEC monitoring (GISTM) systems recordings at North pole [Himadri station; Geographic 78°55′ N, 11°56′ E] and South pole [Maitri station; Geographic 70°46′ S 11°44′ E]. Observations show the range of %TEC variability being relatively more over Antarctic region (−40 % to 60 %) than Arctic region (−25 % to 25 %), corroborating the role of the dominant solar photoionization production process. Our analysis confirms that TEC variation at polar latitudes is a function of magnetosphere-ionosphere coupling, depending on interplanetary magnetic field (IMF) orientation and magnitude in the X ( B x Bx ), Y ( B y By ), and Z ( B z Bz ) plane. Visible enhancement in TEC is noticed in the northern polar latitude when B x < 0 Bx<0 , B y < − 6 nT By<-6\hspace{0.1667em}\text{nT} or B y > 6 nT By>6\hspace{0.1667em}\text{nT} and B z > 0 Bz>0 whereas the southern polar latitude perceives TEC enhancements with B x > 0 Bx>0 , − 6 nT < B y < 6 nT -6\hspace{0.1667em}\text{nT}<By<6\hspace{0.1667em}\text{nT} and B z < 0 Bz<0 . Further investigation reveals the intensity of phase scintillation being more pronounced than the amplitude scintillation during the disturbed geomagnetic conditions with excellent correlation with the temporal variation of TEC at both the stations. Corresponding variations in the parameters are studied in terms of particle precipitation, auroral oval expansion, Joule’s heating phenomena, and other ionospheric parameters. The studies are in line with efforts for improving ionospheric delay error and scintillation modeling and satellite-based positioning accuracies in polar latitudes.

Theory and observations of switchbacks’ evolution in the solar wind

2021 ◽  
Author(s):  
Anna Tenerani ◽  
Marco Velli ◽  
Lorenzo Matteini
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Radial Magnetic Field ◽  
Open Questions ◽  
Coronal Activity ◽  
Turbulent Heating ◽  
Field Lines ◽  
Radial Evolution ◽  
Field Correlation

&lt;p&gt;Alfv&amp;#233;nic fluctuations represent the dominant contributions to turbulent fluctuations in the solar wind, especially, but not limited to, the fastest streams with velocity of the order of 600-700 km/s. Alfv&amp;#233;nic fluctuations can contribute to solar wind heating and acceleration via wave pressure and turbulent heating. Observations show that such fluctuations are characterized by a nearly constant magnetic field amplitude, a condition which remains largely to be understood and that may be an indication of how fluctuations evolve and relax in the expanding solar wind. Interestingly, measurements from Parker Solar Probe have shown the ubiquitous and persistent presence of the so-called switchbacks. These are magnetic field lines which are strongly perturbed to the point that they produce local inversions of the radial magnetic field. The corresponding signature of switchbacks in the velocity field is that of local enhancements in the radial speed (or jets) that display the typical velocity-magnetic field correlation that characterizes Alfv&amp;#233;n waves propagating away from the Sun.&amp;#160;While there is not yet a general consensus on what is the origin of switchbacks and their connection to coronal activity, a first necessary step to answer these important questions is to understand how they evolve and how long they can persist in the solar wind. Here we investigate the evolution of switchbacks. We address how their evolution is affected by parametric instabilities and the possible role of expansion, by comparing models with the observed radial evolution of the fluctuations&amp;#8217; amplitude. We finally discuss what are the implications of our results for models of switchback generation and related open questions.&lt;/p&gt;

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