CONFERENCES

SPD -AAS , June 2004

The presentation can be downloaded here
TITLE: Optical Observations of Flare-induced Oscillations

ABSTRACT: We present high-cadence Ha blue wing observations of a C9.6 solar flare obtained at Big Bear Solar Observatory (BBSO) on 25 August 2001 using the Rapid Dual Imager (RDI). Wavelet and time-distance analysis methods were used to study oscillatory power along the ribbon, finding periods of 40-80 sec during the impulsive phase of the flare. A parametric study of the lightcurves found statistically significant intensity oscillations with amplitudes of ~3% of the peak flare amplitude, periods of ~69 sec and decay times of ~500 sec. These measured properties are consistent with the existence of flare-generated acoustic waves within the overlying loops.

Other work presented:
Active Region Evolution and Activity During the Storms of Halloween 2003
Gallagher, McAteer

SOHO 13 Waves, oscillations and small scale transient events in the solar atmosphere.
A joint view of SOHO and TRACE, Mallorca, 29 Sep. - 4 Oct., 2003

The presentation can be downloaded here
TITLE: An Automated Wavelet Analysis Approach to TRACE Quiet Sun Oscillations

ABSTRACT: An automated wavelet analysis approach to TRACE UV quiet Sun datasets is discussed. Periodicity and lifetime of oscillations present in the network and internetwork are compared and contrasted. This provides a means of extending previous Fourier results into the time-localised domain. The longest lifetime oscillations occur around the acoustic band and the network tends to dominate over the internetwork at periods greater than 4 mins. However, it is shown that the internetwork can dominate over the network at long periods (7 - 20~mins), but only for short lifetimes (less than 3 complete oscillations). These results are discussed in terms of chromospheric heating theories.

Other work presented:
Oscillatory Signatures Above Quiet Sun Magnetic Elements
Bloomfield, Lites, Judge, McAteer, Mathioudakis, Keenan
Preliminary results for SECIS observations of the 2001 eclipse
Katsiyannis, Williams, McAteer, Murtagh, Gallagher

Publications resulting from this conference are available here

National Astronomy Meeting, Dublin, 7-11 April, 2003

The oral presentation can be downloaded here
A description of UKSP at NAM can be downloaded here
TITLE: Wavelet Analysis of the Quiet Sun

ABSTRACT: Oscillatory power in the quiet sun network and internetwork is compared and contrasted in four TRACE wavebands (1216, 1550, 1600,1700). A new and innovative use of wavelet analysis is used to discover the distribution of frequencies and durations of any significant oscillatory motions. This new approach allows an automated wavelet analysis of almost one million lightcurves. Initial results show a definite distinction between network and internetwork regions, with improved statistical significance over previous Fourier analysis.

Posters presented:
Travelling MHD waves in the Quiet Sun
Bloomfield, McAteer, Mathiuodakis, Lites, Williams, Keenan
Detections of high-frequency oscillations in solar active region coronal loops
Katsiyannis, Williams, McAteer, Gallagher, Keenan

Magnetic Coupling of the Solar Atmosphere, Santorini, Greece, 11 - 15 June 2002,

The oral presentation can be downloaded here.
I also presented this talk at Queen's University Belfast as part of the APS seminar series.
TITLE: Detection of Propagating Waves in Network Bright Points Throughout the Chromosphere

ABSTRACT: We analysed oscillations in individual Network Bright Points (NBPs) in Ca II K3, H-alpha, Mg i b2, and Mg i b1- 0.4 angstroms giving us a range of heights from the upper to lower chromosphere. Lightcurves, and hence power spectra, were created by isolating distinct regions of the NBP via a simple intensity thresholding technique. Using this technique, it was possible to identify peaks in the power spectra with particular spatial positions within the NBPs. This was extended into the time domain by means of wavelet analysis. We track the temporal evolution of power in particular frequency bands by creating `power curves'. These are then cross-correlated across all observed wavelengths to search for propagating waves.
In particular, long-period waves with periods of 4-15 minutes (1-4 mHz) were found in the central portion of each NBP, indicating that these waves are certainly not acoustic, but possibly due to magneto-acoustic or magneto-gravity wave modes. We note the possible existence of fast-mode MHD waves in the lower chromosphere, coupling and transferring power to higher-frequency slow-mode MHD waves in the upper chromosphere.

Posters presented:
Observations of a high-frequency fast-mode wave in a coronal loop
Williams, Mathioudakis, Gallagher, Phillips, McAteer, Keenan, Katsiyannis
Detections of high-frequency oscillations in solar active region coronal loops
Katsiyannis, Williams, McAteer, Gallagher, Keenan

Publications resulting from this conference can be found here

Coordinated Data Analysis Workshop, Washington DC, August 2002

National Astronomy Meeting, Cambridge, April, 2001