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Drift-induced perpendicular transport of Solar Energetic Particles  

Mike Marsh   Submitted: 2013-07-04 09:31

Drifts are known to play a role in galactic cosmic ray transport within the heliosphere and are a standard component of cosmic ray propagation models. However, the current paradigm of Solar Energetic Particle (SEP) propagation holds the effects of drifts to be negligible, and they are not accounted for in most current SEP modelling efforts. We present full-orbit test particle simulations of SEP propagation in a Parker spiral interplanetary magnetic field which demonstrate that high energy particle drifts cause significant asymmetric propagation perpendicular to the interplanetary magnetic field. Thus in many cases the assumption of field aligned propagation of SEPs may not be valid. We show that SEP drifts have dependencies on energy, heliographic latitude, and charge to mass ratio, that are capable of transporting energetic particles perpendicular to the field over significant distances within interplanetary space, e.g. protons of initial energy 100 MeV propagate distances across the field on the order of 1 AU, over timescales typical of a gradual SEP event. Our results demonstrate the need for current models of SEP events to include the effects of particle drift. We show that the drift is considerably stronger for heavy ion SEPs due to their larger mass to charge ratio. This paradigm shift has important consequences for the modelling of SEP events and is crucial to the understanding and interpretation of in-situ observations.

Authors: M. S. Marsh, S. Dalla, J. Kelly, and T. Laitinen
Projects:

Publication Status: Accepted for publication in ApJ
Last Modified: 2013-07-10 13:41
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Observed damping of the slow magnetoacoustic mode  

Mike Marsh   Submitted: 2011-04-07 03:43

Spectroscopic and stereoscopic imaging observations of slow magnetoacoustic wave propagation within a coronal loop are investigated to determine the decay length scale of the slow magnetoacoustic mode in three dimensions and the density profile within the loop system. The slow wave is found to have an e-folding decay length scale of 20,000+4000-3000km with a uniform density profile along the loop base. These observations place quantitive constraints on the modelling of wave propagation within coronal loops. Theoretical forward modelling suggests that magnetic field line divergence is the dominant damping factor and thermal conduction is insufficient, given the observed parameters of the coronal loop temperature, density and wave mode period.

Authors: M. S. Marsh, I. De Moortel, and R. W. Walsh
Projects: STEREO

Publication Status: Accepted for publication in ApJ
Last Modified: 2011-04-07 03:43
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Confirming a Seismologically Inferred Coronal Temperature  

Mike Marsh   Submitted: 2009-10-20 06:33

The Extreme-Ultraviolet Imaging Spectrometer on board the HINODE satellite is used to examine the loop system described in Marsh et al. (2009) by applying spectroscopic diagnostic methods. A simple isothermal mapping algorithm is applied to determine where the assumption of isothermal plasma may be valid, and the emission measure locii technique is used to determine the temperature profile along the base of the loop system. It is found that, along the base, the loop has a uniform temperature profile with a mean temperature of 0.89 +- 0.09 MK which is in agreement with the temperature determined seismologically in Marsh et al. (2009), using observations interpreted as the slow magnetoacoustic mode. The results further strengthen the slow mode interpretation, propagation at a uniform sound speed, and the analysis method applied in Marsh et al. (2009). It is found that it is not possible to discriminate between the slow mode phase speed and the sound speed within the precision of the present observations.

Authors: M.S. Marsh and R.W. Walsh
Projects: Hinode/EIS

Publication Status: ApJL, 2009, 706, 76
Last Modified: 2009-11-02 07:54
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3D Coronal Slow Modes: Towards 3D Seismology  

Mike Marsh   Submitted: 2009-03-25 04:58

On 2008 January 10, the twin Solar Terrestrial Relations Observatory (STEREO) A and B spacecraft conducted a high time cadence study of the solar corona with the Extreme UltraViolet Imager (EUVI) instruments with the aim of investigating coronal dynamics. Observations of the three-dimensional propagation of waves within active region coronal loops and a measurement of the true coronal slow mode speed are obtained. Intensity oscillations with a period of approximately 12 minutes are observed to propagate outwards from the base of a loop system, consistent with the slow magnetoacoustic mode. A novel analysis technique is applied to measure the wave phase velocity in the observations of the A and B spacecraft. These stereoscopic observations are used to infer the three-dimensional velocity vector of the wave propagation, with an inclination of 37 +- 6 deg to the local normal and a magnitude of 132 +- 9 and 132 +- 11 km s-1, giving the first measurement of the true coronal longitudinal slow mode speed, and an inferred temperature of 0.84 +- 12 MK and 0.84 +- 15 MK.

Authors: M. S. Marsh, R. W. Walsh, S. Plunkett
Projects: STEREO

Publication Status: In press, ApJ June 2009 - 1 v697 issue
Last Modified: 2009-03-25 10:04
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p-Mode Propagation through the Transition Region into the Solar Corona. I. Observations  

Mike Marsh   Submitted: 2009-01-20 04:54

Oscillations have long been observed in the sunspot umbral chromosphere and transition region, connected to global p-mode oscillations. These p-modes are thought to undergo mode conversion to slow magnetoacoustic waves in regions of strong magnetic field. More recently, propagating oscillations have also been observed in solar coronal loops. Using new spectroscopic imaging data at transition-region temperatures, combined with coronal imaging, we present direct observations of the propagation of these slow magnetoacoustic p-modes through the transition region and into the solar corona, along the magnetic field. The waves are observed as oscillations in the chromosphere/transition region and propagations in the corona due to the emission scale height of the different temperature lines combined with the magnetic field geometry.

Authors: M. S. Marsh and R. W. Walsh
Projects: SoHO-CDS

Publication Status: ApJ 2006 643 540-548
Last Modified: 2009-01-20 08:22
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Bayesian Analysis of Solar Oscillations  

Mike Marsh   Submitted: 2008-07-03 09:27

A Bayesian probability-based approach is applied to the problem of detecting and parameterizing oscillations in the upper solar atmosphere for the first time. Due to its statistical origin, this method provides a mechanism for determining the number of oscillations present, gives precise estimates of the oscillation parameters with a self-consistent statistical error analysis, and allows the oscillatory model signals to be reconstructed within these errors. A highly desirable feature of the Bayesian approach is the ability to resolve oscillations with extremely small frequency separations. The code is applied to SOHO CDS O v λ629 observations and resolves four distinct p4, p5, p6, and p7, p-modes within the same sunspot transition region. This suggests that a spectrum of photospheric p-modes is able to propagate into the upper atmosphere of the Sun and Sun-like stars, and places precise observational constraints on models of umbral eigenmodes.

Authors: M. S. Marsh, J. Ireland, and T. Kucera
Projects: SoHO-CDS

Publication Status: The Astrophysical Journal, 681:672?679, 2008 July 1
Last Modified: 2008-09-23 20:57
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Joint CDS and Trace Observations of Active Region Dynamics  

Mike Marsh   Submitted: 2005-11-21 08:57

A sunspot active region is imaged with the Coronal Diagnostic Spectrometer (CDS) and Transition Region and Coronal Explorer (TRACE). We use the CDS wide slit to image the active region in He I 584 A, O V 629 A and Mg IX 368 A and co-temporally in the TRACE 171 Å passband. 3-min oscillations are observed above the sun-spot umbra in He I and O V. These oscillations are then observed to propagate along the active region loops observed in TRACE with a velocity component of 80 km s-1. We suggest that the 3-min sunspot oscillations in CDS and the propagations in TRACE are the same wave phenomena. The waves are observed as oscillations in the chromosphere/transition region and propagations in the corona due to line of sight effects of the magnetic field geometry combined with the line formation height of the different temperature lines.

Authors: Marsh, M. S.; Walsh, R. W.
Projects: Soho-CDS,TRACE

Publication Status: Proceedings of the SOHO 15 Workshop - Coronal Heating. 6-9 September 2004, St. Andrews, Scotland, UK (ESA SP-575). Editors: R.W. Walsh, J. Ireland, D. Danesy, B. Fleck. Paris: European Space Agency, 2004., p.108
Last Modified: 2005-11-21 08:57
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Longitudinal Oscillations in Coronal Loops - Joint Observations with SOHO/CDS and TRACE  

Mike Marsh   Submitted: 2005-11-21 08:54

Joint Observing Program (JOP) 83 Solar and Heliospheric Observatory/Coronal Diagnostic Spectrometer (SOHO/CDS) and Transition Region and Coronal Explorer (TRACE) data is analysed for evidence of propagating intensity oscillations along loop structures in the solar corona. A propagating intensity oscillation with a minimum estimated speed of 50-195 km s is observed within a TRACE 171 Å coronal loop using a running difference method. Co-spatial and co-temporal CDS and TRACE observations of this loop are analysed using a wavelet analysis method. The TRACE data shows a propagating oscillation with a period of 300 s. This period is also observed with CDS suggesting propagating oscillations at chromospheric, transition region and coronal temperatures in the He I, O V and Mg IX lines.

Authors: Marsh, M. S.; Walsh, R. W.; de Moortel, I.; Ireland, J.
Projects: Soho-CDS,TRACE

Publication Status: Proceedings of 'SOHO 13 - Waves, Oscillations and Small-Scale Transient Events in the Solar Atmosphere: A Joint View from SOHO and TRACE'. 29 September - 3 October 2003, Palma de Mallorca, Balearic Islands, Spain (ESA SP-547, January 2004). Compiled by: H
Last Modified: 2005-11-21 08:54
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Joint observations of propagating oscillations with SOHO/CDS and TRACE  

Mike Marsh   Submitted: 2005-11-21 08:52

Joint Observing Program (JOP) 83 Solar and Heliospheric Observatory/Coronal Diagnostic Spectrometer (SOHO/CDS) and Transition Region and Coronal Explorer (TRACE) data is analysed for evidence of propagating intensity oscillations along loop structures in the solar corona. A propagating intensity oscillation with a minimum estimated speed of 50-195 km s-1 is observed within a TRACE 171 Å coronal loop using a running difference method. Co-spatial and co-temporal CDS and TRACE observations of this loop are analysed using a wavelet analysis method. The TRACE data shows a propagating oscillation with a period of ~300 s. This period is also observed with CDS suggesting propagating oscillations at chromospheric, transition region and coronal temperatures in the He I, O V and Mg Ix lines.

Authors: Marsh, M. S.; Walsh, R. W.; De Moortel, I.; Ireland, J.
Projects: Soho-CDS,TRACE

Publication Status: Astronomy and Astrophysics, v.404, p.L37-L41 (2003)
Last Modified: 2005-11-21 08:52
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Observations of time dependent periodicity within the coronal hole boundary  

Mike Marsh   Submitted: 2005-11-21 08:51

High time resolution (≍13 sec cadence) Solar and Heliospheric Observatory (SOHO) Coronal Diagnostic Spectrometer (CDS) Grazing Incidence Spectrometer (GIS) time series data is analysed for evidence of quasi-periodic variability in the solar corona. The observations are obtained from a GIS study of a coronal hole boundary region taken in October 1997. A wavelet analysis is applied to EUV emission lines covering a temperature range of log Te = 5.3-6.1K. Wavelet analysis allows the frequency and temporal information of any periods present within the data to be analysed. Observations are presented of a time dependent periodicity positioned over a chromospheric network position located at the boundary position of a coronal hole.

Authors: Marsh, M. S.; Walsh, R. W.; Bromage, B. J. I.
Projects: Soho-CDS

Publication Status: In: SOLMAG 2002. Proceedings of the Magnetic Coupling of the Solar Atmosphere Euroconference and IAU Colloquium 188, 11 - 15 June 2002, Santorini, Greece. Ed. H. Sawaya-Lacoste. ESA SP-505. Noordwijk, Netherlands: ESA Publications Division, ISBN 92-9092-8
Last Modified: 2005-11-21 08:51
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A wavelet analysis of quasi-periodic variability across a solar coronal hole region  

Mike Marsh   Submitted: 2005-11-21 08:49

High time resolution (~13 s cadence) Solar and Heliospheric Observatory (SOHO) Coronal Diagnostic Spectrometer (CDS) Grazing Incidence Spectrometer (GIS) time series data is analysed for evidence of quasi-periodic variability in the solar corona. The observations are obtained from a GIS study of a coronal hole boundary region taken in October 1997. A wavelet analysis is applied to EUV emission lines covering a temperature range of log Te= 5.3-6.1 K. Wavelet analysis allows the frequency and temporal information of any periods present within the data to be analysed. Statistically significant periods are found within the range 100-900 s and 1500 s. Observations of short wavepackets with periods of the order 50-100 s with durations of 2-5 cycles are reported. Observations of a decay in the driving period over time are also described.

Authors: Marsh, M. S.; Walsh, R. W.; Bromage, B. J. I.
Projects: Soho-CDS

Publication Status: Astronomy and Astrophysics, v.393, p.649-659 (2002)
Last Modified: 2005-11-21 08:49
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A wavelet analysis of quasi-periodic variability within the solar corona  

Mike Marsh   Submitted: 2005-11-21 08:47

High time resolution (≍13 sec cadence) Solar and Heliospheric Observatory (SOHO) Coronal Diagnostic Spectrometer (CDS) Grazing Incidence Spectrometer (GIS) time series data is analysed for evidence of quasi-periodic variability in the solar corona. The observations are obtained from a GIS study of a coronal hole boundary region taken in October 1997. A wavelet anaylsis is applied to EUV emission lines covering a temperature range of log Te = 5.3 - 6.1K. Wavelet analysis allows the frequency and temporal information of any periods present within the data to be analysed. Statistically significant periods are found within the range 100 - 900 seconds. Observations of short wavepackets with periods of the order 50 - 100 seconds with durations of 2 - 5 oscillations are reported.

Authors: Marsh, M. S.; Walsh, R. W.; Bromage, B. J. I.
Projects: Soho-CDS

Publication Status: In: Proceedings of the SOHO 11 Symposium on From Solar Min to Max: Half a Solar Cycle with SOHO, 11-15 March 2002, Davos, Switzerland. A symposium dedicated to Roger M. Bonnet. Edited by A. Wilson, ESA SP-508, Noordwijk: ESA Publications Division, ISBN 92
Last Modified: 2005-11-21 08:47
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Abstracts by Author
Drift-induced perpendicular transport of Solar Energetic Particles
Observed damping of the slow magnetoacoustic mode
Confirming a Seismologically Inferred Coronal Temperature
3D Coronal Slow Modes: Towards 3D Seismology
p-Mode Propagation through the Transition Region into the Solar Corona. I. Observations
Bayesian Analysis of Solar Oscillations
Joint CDS and Trace Observations of Active Region Dynamics
Longitudinal Oscillations in Coronal Loops - Joint Observations with SOHO/CDS and TRACE
Joint observations of propagating oscillations with SOHO/CDS and TRACE
Observations of time dependent periodicity within the coronal hole boundary
A wavelet analysis of quasi-periodic variability across a solar coronal hole region
A wavelet analysis of quasi-periodic variability within the solar corona

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