scholarly journals Mars photoelectron energy and pitch angle dependence on intense lower atmospheric dust storms

2014 ◽  
Vol 119 (7) ◽  
pp. 1689-1706 ◽  
Author(s):  
Shaosui Xu ◽  
Michael W. Liemohn ◽  
David L. Mitchell ◽  
Michael D. Smith
Keyword(s):  
Pitch Angle ◽  
Dust Storms ◽  
Atmospheric Dust ◽  
Angle Dependence ◽  
Photoelectron Energy

scholarly journals Long-term variability of dust events in Iceland (1949–2011)

2014 ◽  
Vol 14 (24) ◽  
pp. 13411-13422 ◽  
Author(s):  
P. Dagsson-Waldhauserova ◽  
O. Arnalds ◽  
H. Olafsson
Keyword(s):  
Particulate Matter ◽  
Volcanic Eruptions ◽  
Dust Storms ◽  
The Arctic ◽  
Atmospheric Dust ◽  
The World ◽  
Icelandic Low ◽  
Dust Events ◽  
The 1960S

Abstract. The long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and interpreted together with earlier results obtained from northeastern (NE) Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust observations. However, frequent volcanic eruptions, with the re-suspension of volcanic materials and dust haze, increased the number of dust events fourfold (135 dust days annually). The position of the Icelandic Low determined whether dust events occurred in the NE (16.4 dust days annually) or in the southern (S) part of Iceland (about 18 dust days annually). The decade with the most frequent dust days in S Iceland was the 1960s, but the 2000s in NE Iceland. A total of 32 severe dust storms (visibility < 500 m) were observed in Iceland with the highest frequency of events during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm, occurring during summer/autumn (May–September) and during mild southwesterly winds, while the subarctic dust events (S Iceland) were mainly cold, occurring during winter/spring (March–May) and during strong northeasterly winds. About half of the dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between particulate matter (PM10) concentrations and visibility during dust observations at the stations Vík and Stórhöfði. This study shows that Iceland is among the dustiest areas of the world and that dust is emitted year-round.

scholarly journals Long-term variability of dust events in Iceland (1949–2011)

2014 ◽  
Vol 14 (11) ◽  
pp. 17331-17358 ◽  
Author(s):  
P. Dagsson-Waldhauserova ◽  
O. Arnalds ◽  
H. Olafsson
Keyword(s):  
Sea Level ◽  
Dust Storms ◽  
The Arctic ◽  
Atmospheric Dust ◽  
Sea Level Pressure ◽  
Term Frequency ◽  
The World ◽  
Dust Events ◽  
The 1960S

Abstract. Long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and merged with results obtained from the Northeast Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust. Including codes 04–06 into the criteria for dust observations, the frequency was 135 dust days annually. The Sea Level Pressure (SLP) oscillation controlled whether dust events occurred in NE (16.4 dust days annually) or in southern part of Iceland (about 18 dust days annually). The most dust-frequent decade in S Iceland was the 1960s while the most frequent decade in NE Iceland was the 2000s. A total of 32 severe dust storms (visibility < 500 m) was observed in Iceland with the highest frequency during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm and during summer/autumn (May–September) while the Sub-Arctic dust events (S Iceland) were mainly cold and during winter/spring (March–May). About half of dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between PM10 concentrations and visibility during dust observations at the stations Vik and Storhofdi. This study shows that Iceland is among the dustiest areas of the world and dust is emitted the year-round.

scholarly journals Pitch Angle Dependence of Electron and Ion Flux Changes During Local Magnetic Dipolarization Inside Geosynchronous Orbit

2020 ◽  
Vol 125 (2) ◽  
Author(s):  
T. Motoba ◽  
S. Ohtani ◽  
M. Gkioulidou ◽  
D. G. Mitchell ◽  
A. Y. Ukhorskiy ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Ion Flux ◽  
Geosynchronous Orbit ◽  
Angle Dependence

scholarly journals Asymmetric impacts on Mars' polar vortices from the 2018 Global Dust Storm

2021 ◽  
Author(s):  
Paul Streeter ◽  
Stephen Lewis ◽  
Manish Patel ◽  
James Holmes ◽  
Anna Fedorova ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Climate Model ◽  
Global Climate Model ◽  
Polar Vortex ◽  
Dust Storms ◽  
The South ◽  
Atmospheric Dust ◽  
The North ◽  
Dust Loading ◽  
Spacecraft Data

&lt;p&gt;&lt;strong&gt;Introduction:&lt;/strong&gt;&amp;#160; Like Earth, Mars possesses dynamical atmospheric features known as polar vortices. These are regions of cold, isolated polar air surrounded by powerful westerly wind jets which can create barriers to transport of atmospheric dust, water, and chemical species. They have a complex and asymmetrical (north/south) relationship with atmospheric dust loading [1]. Regional and global dust events have been shown to cause rapid vortex displacement [2,3] in the northern vortex, while the southern vortex appears more robust.&lt;/p&gt; &lt;p&gt;Unlike Earth, Mars also experiences planet-encircling Global Dust Storms: spectacular, planet-spanning events which dramatically increase atmospheric dust loading. The most recent such event in 2018 (beginning at northern autumn equinox) [4] was observed by multiple spacecraft, including the ExoMars Trace Gas Orbiter (TGO) and the Mars Reconnaissance Orbiter (MRO), enabling the opportunity to study its effects on the polar vortices in detail.&lt;/p&gt; &lt;p&gt;We do this by assimilating [5] spacecraft data from TGO&amp;#8217;s Atmospheric Chemistry Suite (ACS) [6,7] and MRO&amp;#8217;s Mars Climate Sounder (MCS) [8,9] into the LMD-UK Mars Global Climate Model [10], a 4D numerical model of the martian atmosphere.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;We present our recently published results [11], where we find that the 2018 GDS had asymmetrical impacts in each hemisphere: the northern polar vortex remained relatively robust, while the southern polar vortex was significantly disrupted. This asymmetry was due to both the storm&amp;#8217;s latitudinal extent, which was greater in the south than in the north, and its timing, occurring as the southern vortex was already decaying after equinox. Both polar vortices and especially the northern showed reductions in their ellipticity, and this correlated with a reduction in high-latitude stationary wave activity in both hemispheres. We show that the characteristic elliptical shape of Mars&amp;#8217; polar vortices is the pattern of the stationary waves; this was suppressed during the storm by the shifting of the polar jet away from regions of high mechanical forcing in the north, and by the reduced polar jet due to the decreased meridional temperature gradient in the south. These asymmetric effects suggest enhanced transport into the southern, but not northern, polar region during GDS around northern autumn equinox, as well as more longitudinally symmetric transport around both poles.&lt;/p&gt; &lt;p&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt; [1] Waugh, D. W. et al (2016) &lt;em&gt;J. Geophys. Res. Planets, 121, &lt;/em&gt;1770-1785. [2] Guzewich, S. D. et al (2016) &lt;em&gt;Icarus, 278, &lt;/em&gt;100-118. [3] Mitchell, D. M. et al (2015) &lt;em&gt;Q.J.R. Meteorol. Soc., 141, &lt;/em&gt;550-562. [4] Kass, D. M et al (2019) &lt;em&gt;GRL, 47&lt;/em&gt;(23). [5] Lewis, S. R. et al (2007) &lt;em&gt;Icarus, 192&lt;/em&gt;(2). [6] Korablev, O. et al (2018) &lt;em&gt;Space Sci. Rev., 214&lt;/em&gt;(7). [7] Fedorova, A. A. et al (2020) &lt;em&gt;Science, 367&lt;/em&gt;(6475). [8] McCleese, D. J. et al (2007) &lt;em&gt;JGR (Planets), 112&lt;/em&gt;(E5). [9] Kleinb&amp;#246;hl, A. et al (2009) &lt;em&gt;JGR (Planets), 114&lt;/em&gt;(E10). [10] Forget, F. et al (1999) &lt;em&gt;JGR (Planets), 104&lt;/em&gt;(E10). [11] Streeter, P. M. et al (2021) &lt;em&gt;JGR (Planets), &lt;/em&gt;e2020JE006774.&lt;/p&gt;

scholarly journals Cross-field transport and pitch-angle anisotropy of solar energetic particles in MHD turbulence

2016 ◽  
Vol 2 ◽  
pp. 63-65 ◽  
Author(s):  
F. Fraschetti
Keyword(s):  
Pitch Angle ◽  
Turbulence Models ◽  
Energetic Particles ◽  
Solar Energetic Particles ◽  
Mhd Turbulence ◽  
First Order ◽  
Angle Dependence ◽  
Inhomogeneous Turbulence ◽  
Angle Scattering

Abstract. Recent modelling of solar energetic particles (SEPs) propagation through the heliospheric turbulence, also discussed in this workshop, has investigated the role of the pitch-angle scattering and the perpendicular transport in spreading particles in heliolongitude, as shown by multi-spacecraft measurements (STEREO A/B, ACE, SOHO, etc.) at 1 AU in various energy ranges. In some events the first-order pitch-angle anisotropy of the particles distribution is not-negligible. We calculate the average perpendicular displacement due to the gradient/curvature drift in an inhomogeneous turbulence accounting for pitch-angle dependence for two MHD turbulence models: (a) 3-D isotropic, (b) anisotropic as conjectured by Goldreich-Sridhar. We find in both cases that the drift scales as (1 − μ2)2 with the cosine of pitch-angle μ, in contrast with previous models for transport of SEPs. This result can impact the models of propagation of SEPs through the heliosphere.

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