22 research outputs found
Role of periodic loadingâunloading in the magnetotail versus interplanetary magnetic field B z flipping in the ring current buildup
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94813/1/jgra19183.pd
Validation for solar wind prediction at Earth: Comparison of coronal and heliospheric models installed at the CCMC
Multiple coronal and heliospheric models have been recently upgraded at the Community Coordinated Modeling Center (CCMC), including the WangâSheeleyâArge (WSA)âEnlil model, MHDâAroundâaâSphere (MAS)âEnlil model, Space Weather Modeling Framework (SWMF), and heliospheric tomography using interplanetary scintillation data. To investigate the effects of photospheric magnetograms from different sources, different coronal models, and different model versions on the model performance, we run these models in 10 combinations. Choosing seven Carrington rotations in 2007 as the time window, we compare the modeling results with the Operating Mission as Nodes on the Internet data for nearâEarth space environment during the late declining phase of solar cycle 23. Visual comparison is proved to be a necessary addition to the quantitative assessment of the models' capabilities in reproducing the time series and statistics of solar wind parameters. The MASâEnlil model captures the time patterns of solar wind parameters better, while the WSAâEnlil model matches with the time series of normalized solar wind parameters better. Models generally overestimate slow wind temperature and underestimate fast wind temperature and magnetic field. Using improved algorithms, we have identified magnetic field sector boundaries (SBs) and slowâtoâfast stream interaction regions (SIRs) as focused structures. The success rate of capturing them and the time offset vary largely with models. For this quiet period, the new version of MASâEnlil model works best for SBs, while heliospheric tomography works best for SIRs. The new version of SWMF with more physics added needs more development. General strengths and weaknesses for each model are diagnosed to provide an unbiased reference to model developers and users.Key PointsPerformance metrics for solar wind simulation are developedTen model combinations are validated with strengths and weaknesses diagnosedStream interactions are captured 30â80% of the time and by 0.5â2.5 days offPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111912/1/swe20222.pd
Validation for global solar wind prediction using Ulysses comparison: Multiple coronal and heliospheric models installed at the Community Coordinated Modeling Center
The prediction of the background global solar wind is a necessary part of space weather forecasting. Several coronal and heliospheric models have been installed and/or recently upgraded at the Community Coordinated Modeling Center (CCMC), including the WangĂą SheelyĂą Arge (WSA)Ăą Enlil model, MHDĂą AroundĂą aĂą Sphere (MAS)Ăą Enlil model, Space Weather Modeling Framework (SWMF), and heliospheric tomography using interplanetary scintillation data. Ulysses recorded the last fast latitudinal scan from southern to northern poles in 2007. By comparing the modeling results with Ulysses observations over seven Carrington rotations, we have extended our thirdĂą party validation from the previous nearĂą Earth solar wind to middle to high latitudes, in the same late declining phase of solar cycle 23. Besides visual comparison, we have quantitatively assessed the modelsâ capabilities in reproducing the time series, statistics, and latitudinal variations of solar wind parameters for a specific range of model parameter settings, inputs, and grid configurations available at CCMC. The WSAĂą Enlil model results vary with three different magnetogram inputs. The MASĂą Enlil model captures the solar wind parameters well, despite its underestimation of the speed at middle to high latitudes. The new version of SWMF misses many solar wind variations probably because it uses lower grid resolution than other models. The interplanetary scintillationĂą tomography cannot capture the latitudinal variations of solar wind well yet. Because the model performance varies with parameter settings which are optimized for different epochs or flow states, the performance metric study provided here can serve as a template that researchers can use to validate the models for the time periods and conditions of interest to them.Key PointsPerformance metrics for the global solar wind prediction are developedEight model combinations are validated with strengths and weaknesses identified for each modelEffect of model internal parameter settings and magnetogram input is discussedPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134247/1/swe20343_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134247/2/swe20343.pd
Buildup of the ring current during periodic loadingâunloading cycles in the magnetotail driven by steady southward interplanetary magnetic field
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95239/1/jgra18825.pd
Multiscale modeling of magnetospheric reconnection
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95438/1/jgra18824.pd
Magnetic Flux of EUV Arcade and Dimming Regions as a Relevant Parameter for Early Diagnostics of Solar Eruptions - Sources of Non-Recurrent Geomagnetic Storms and Forbush Decreases
This study aims at the early diagnostics of geoeffectiveness of coronal mass
ejections (CMEs) from quantitative parameters of the accompanying EUV dimming
and arcade events. We study events of the 23th solar cycle, in which major
non-recurrent geomagnetic storms (GMS) with Dst <-100 nT are sufficiently
reliably identified with their solar sources in the central part of the disk.
Using the SOHO/EIT 195 A images and MDI magnetograms, we select significant
dimming and arcade areas and calculate summarized unsigned magnetic fluxes in
these regions at the photospheric level. The high relevance of this eruption
parameter is displayed by its pronounced correlation with the Forbush decrease
(FD) magnitude, which, unlike GMSs, does not depend on the sign of the Bz
component but is determined by global characteristics of ICMEs. Correlations
with the same magnetic flux in the solar source region are found for the GMS
intensity (at the first step, without taking into account factors determining
the Bz component near the Earth), as well as for the temporal intervals between
the solar eruptions and the GMS onset and peak times. The larger the magnetic
flux, the stronger the FD and GMS intensities are and the shorter the ICME
transit time is. The revealed correlations indicate that the main quantitative
characteristics of major non-recurrent space weather disturbances are largely
determined by measurable parameters of solar eruptions, in particular, by the
magnetic flux in dimming areas and arcades, and can be tentatively estimated in
advance with a lead time from 1 to 4 days. For GMS intensity, the revealed
dependencies allow one to estimate a possible value, which can be expected if
the Bz component is negative.Comment: 27 pages, 5 figures. Accepted for publication in Solar Physic
Review of solar energetic particle models
Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earthâs protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data.</p
Resonance phenomena in microwave nonmagnetized plasma source. Plasmachemical application
Scheme of coaxial microwave gas-discharge plasma source based on a
âplasma resonanceâ phenomenon is presented. Possibility of conditions
realization at which energy of accelerated in the âresonanceâ electrons
goes into ionization processes (in volume of chamber outside of
âresonanceâ region) is discussed. Results of experimental investigation of
a coaxial microwave plasmatron in which âresonanceâ mechanisms have been
manifested are presented. A plasmachemical reactor based on a âresonanceâ
plasmatron is described. The data on plasmachemical decomposition of
CF2Cl2 are displayed