Space Weather

This slide presentation reviews the hazards and effects of space weather on earth and in space to humans and manmade systems

When Earth Songs Filled the Void of Space

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Solar Eclipse 101: Radio and Photographic Observations

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Laboratory Experiments on Astrophysical Dust Analogs at NASA/MSFC

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Evidence for potential and inductive convection during intense geomagnetic events using normalized superposed epoch analysis

The relative contribution of storm‐time ring current development by convection driven by either potential or inductive electric fields has remained an unresolved question in geospace research. Studies have been published supporting each side of this debate, including views that ring current buildup is entirely one or the other. This study presents new insights into the relative roles of these storm main phase processes. We perform a superposed epoch study of 97 intense ( Dst Min    Dst Min  > –100 nT) storms using OMNI solar wind and ground‐based data. Instead of using a single reference time for the superpositioning of the events, we choose four reference times and expand or contract each phase of every event to the average length of this phase, creating a normalized timeline for the superposed epoch analysis. Using the bootstrap method, we statistically demonstrate that timeline normalization results in better reproduction of average storm dynamics than conventional methods. Examination of the Dst reveals an inflection point in the intense storm group consistent with two‐step main phase development, which is supported by results for the southward interplanetary magnetic field and various ground‐based magnetic indices. This two‐step main‐phase process is not seen in the moderate storm timeline and data sets. It is determined that the first step of Dst development is due to potential convective drift, during which an initial ring current is formed. The negative feedback of this hot ion population begins to limit further ring current growth. The second step of the main phase, however, is found to be a more even mix of potential and inductive convection. It is hypothesized that this is necessary to achieve intense storm Dst levels because the substorm dipolarizations are effective at breaking through the negative feedback barrier of the existing inner magnetospheric hot ion pressure peak. Key Points Moderate and intense geomagnetic storms Evidence for potential and inductive convection Normalized superposed epoch analysisPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97285/1/jgra50014.pd

Dependence of plasmaspheric morphology on the electric field description during the recovery phase of the 17 April 2002 magnetic storm

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95341/1/jgra17301.pd

Correlation Between Low Frequency Auroral Kilometric Radiation (AKR) and Auroral Structures

Auroral Kilometric Radiation (AKR) is a radio wave emission that has long been associated with auroral activity. AKR is normally observed in the frequency range from -60 - 600 kHz. Low frequency AKR (or LF-AKR) events are characterized as a rapid extension of AKR related emissions to 30 kHz or lower in frequency for typically much less than 10 minutes. LF-AKR emissions predominantly occur within a frequency range of 20 kHz - 30 kHz, but there are LF-AKR related emissions that reach to a frequency of 5 kHz. This study correlates all instances of LF-AKR events during the first four years of observations from the IMAGE spacecraft's Radio Plasma Imager (WI) instrument with auroral observations from the wideband imaging camera (WIC) onboard IMAGE. The correlation between LF-AKR occurrence and WIC auroral observations shows that in the 295 confirmed cases of LF-AKR emissions, bifurcation of the aurora is seen in 74% of the cases. The bifurcation is seen in the dusk and midnight sectors of the auroral oval, where AKR is believed to be generated. The polarization of these LF-AKR emissions has yet to be identified. Although LF-AKR may not be the only phenomena correlated with bifurcated auroral structures, bifurcation will occur in most instances when LF-AKR is observed. The LF-AKR emissions may be an indicator of specific auroral processes sometimes occurring during storm-time conditions in which field-aligned density cavities extend a distance of perhaps 5-6 RE tailward from the Earth for a period of 10 minutes or less

Multi-wavelength observations and modelling of a canonical solar flare

This paper investigates the temporal evolution of temperature, emission measure, energy loss and velocity in a C-class solar flare from both an observational and theoretical perspective. The properties of the flare were derived by following the systematic cooling of the plasma through the response functions of a number of instruments -- RHESSI (>5 MK), GOES-12 (5-30 MK), TRACE 171 A (1 MK) and SOHO/CDS (~0.03-8 MK). These measurements were studied in combination with simulations from the 0-D EBTEL model. At the flare on-set, upflows of ~90 km s-1 and low level emission were observed in Fe XIX, consistent with pre-flare heating and gentle chromospheric evaporation. During the impulsive phase, upflows of ~80 km s-1 in Fe XIX and simultaneous downflows of 20 km s-1 in He I and O V were observed, indicating explosive chromospheric evaporation. The plasma was subsequently found to reach a peak temperature of ~13 MK in approximately 10 minutes. Using EBTEL, conduction was found to be the dominant loss mechanism during the initial ~300s of the decay phase. It was also found to be responsible for driving gentle chromospheric evaporation during this period. As the temperature fell below ~8 MK, and for the next ~4,000s, radiative losses were determined to dominate over conductive losses. The radiative loss phase was accompanied by significant downflows of <40 km s-1 in O V. This is the first extensive study of the evolution of a canonical solar flare using both spectroscopic and broad-band instruments in conjunction with a hydrodynamic model. While our results are in broad agreement with the standard flare model, the simulations suggest that both conductive and non-thermal beam heating play important roles in heating the flare plasma during the impulsive phase of at least this event.Comment: 10 pages, 7 figures, 2 tables. Accepted for publication in A&

Shade and Drought Stress-Induced Changes in Phenolic Content of Wild Oat (Avena fatua L.) Seeds

Plants develop under a wide range of maternal environments, depending on the time of emergence, prevailing competition from other plants, and presence or absence of other biotic or abiotic stress factors. Stress factors, such as light limitation and drought, during plant development typically reduces the reproductive allocation to seeds, resulting in fewer and often smaller seeds. Such stress factors may also influence seed quality traits associated with persistence in the soil, such as seed dormancy and chemical defense. For this research, we hypothesized that light limitation and drought during wild oat (Avena fatua L.) seed development would result in reduced allocation to seed phenolics and other aliphatic organic acids previously identified in the seeds of this species. Wild oat isolines (M73 and SH430) were grown in the greenhouse under cyclic drought conditions (2005 only) or two levels of shade (50 and 70%; 2005 and 2006) achieved with standard black shade cloth. The soluble and cellular bound chemical constituents were identified and quantified using gas chromatography - mass spectrometry. The shade and drought stress treatments often significantly affected the mass of the caryopsis and hull seed fractions, as well as the phenolic content of these seed fractions, depending upon isoline, seed fraction, phenolic fraction, and specific phenolics analyzed. Phenolic content of the hull was reduced by the stress environments by up to 48%, whereas there was some evidence of an increase in the soluble phenolic content of the caryopsis in response to the stress environments. Ferulic and p-coumaric acids were the most abundant phenolic acids in both soluble and bound fractions, and bound phenolics comprised generally 95% or more of total phenolics. There was no discernable evidence that the aliphatic organic content was affected by the stress environments. Our results indicate that plant stress during seed development can reduce both the physical and chemical defense in seeds, which may result in seeds that are less persistent in the soil seed bank and potentially less of a weed management concern

A new solar windâ driven global dynamic plasmapause model: 2. Model and validation

A new solar windâ driven global dynamic plasmapause (NSWâ GDP) model has been constructed based on the largest currently available database containing 49,119 plasmapause crossing locations and 3957 plasmapause profiles (corresponding to 48,899 plasmapause locations), from 18 satellites during 1977â 2015 covering four solar cycles. This model is compiled by the Levenbergâ Marquardt method for nonlinear multiparameter fitting and parameterized by VSW, BZ, SYMâ H, and AE. Continuous and smooth magnetic local time dependence controlled mainly by the solar windâ driven convection electric field ESW is also embedded in this model. Compared with previous empirical models based on our database, this new model improves the forecasting accuracy and capability for the global plasmapause. The diurnal, seasonal, and solar cycle variations of the plasmapause can be captured by the new model. The NSWâ GDP model can potentially be used to forecast the global plasmapause shape with upstream solar wind and interplanetary magnetic field parameters and corresponding predicted values of SYMâ H and AE and can also be used as input parameters for other inner magnetospheric coupling models, such as dynamic radiation belt and ring current models and even MHD models.Key PointsA new solar windâ driven global dynamic plasmapause model based on multisatellite observations is constructedThis model is parameterized by VSW, interplanetary magnetic field BZ, SYMâ H, and AE and has continuous and smooth MLT dependenceThis model is potentially applicable to inner magnetospheric research studies and space weather forecastsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138428/1/jgra53619.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138428/2/jgra53619_am.pd