Timothy David - Presenter Profile

Space weather influences our modern, technologically complex systems - including radio communication, communication satellites, and electrical power systems. Imagine how you would feel if you find yourself just like the Biblical Egyptians, in an unannounced darkness for some hours or perhaps days. Worse still, if your Global Positioning System (GPS) refuses to work and the world-presently a global village, returns to the medieval period!

In this article,Timothy David presents his research about the effect of space weather on modern technology.

About My Research

A way of mitigating space weather effects is to slow down its convention across the earth. The earth upper atmosphere does this by loading the magnetosphere (the magnetic cavity that shields the earth from direct impact of solar wind) with heavy ions. As a result of the magnetosphere-ionosphere coupling, the outflowing ionospheric plasma found in the magnetosphere can cause a mass loading of the magnetosphere resulting in various phenomena such as:

  • momentum reduction and energy transfer rates;
  • decreased Alfvén speed caused by heavy oxygen ion (O+) ;
  • slower response time of the magnetosphere to external drivers, et cetera.

Important questions arising from the outflows that need to be addressed are:

  • How do heavy ions become accelerated sufficiently to overcome the effects of Earth’s gravity?
  • What geophysical conditions are required for ion outflows to occur?
  • What are the maximum outflowing ion-fluxes driven by geomagnetic storm-time conditions?

This research is approached by analysing large datasets from satellite missions to identify plasma outflows and combine those observations with others from ground based radars as they observe the plasma upwellings in the ionosphere, some of which are accelerated into the magnetosphere. At first, seven events are considered at a time that the Fast Auroral SnapshoT (FAST) satellite and EISCAT Svalbard radar (ESR) simultaneously detected ion upflow, and this is validated by ground base radars called, Cooperative UK Twin Located Auroral Sounding System (CUTLASS). Analyses of ESR data would provide answer to the problem of determining the maximum outflowing ion fluxes as well as the mechanisms associated with the energization of the heavy ions to overcome earth’s gravity. In addition, data are sourced from OMNIweb to take care of the question on geophysical conditions that are required for ion outflows to occur and also to throw more light on additional input from external factors that accelerate the heavy ions. This work intends to constrain models for the outflows, but large number of events, when ion upwellings and outflows are simultaneously detected is required, so as to have a large database for a robust statistical analysis.

Solar wind_magnetosphereCity blackout

You can see the interaction between the solar wind and Earth's magnetosphere (left) and its effect on the life in a modern city (right).

My Festival Presentation

This work has looked into the plasma outflow from the Earth’s upper atmosphere at inspect of time in seven different events, using FAST-ESR conjunction as the basis and validating the results with the CUTLASS ground base radars and magnetometers, for a time interval covering the whole lifespan of FAST spacecraft. The main results of ESR observation and geophysical conditions around the time of conjunctions are summarized as follows:

  • ESR observed electron precipitation and enhanced electron and ion temperatures during an outflow.
  • The peak upwelling ion fluxes observed are ~1013 m-2 s-1 at altitudes ≥ 300 km.
  • CUTLASS radar indicated cusp signature in the 2006-03-18 event. Also line-of-sight velocity moving towards the radar is identified in the 2002-01-20 event, which is the only nightside event.
  • The statistical analysis of the OMNI data showed the 2006-03-18 event as the period of most effective solar wind disturbance while 2005-09-12 is the period of most magnetospheric disturbance.
  • The coupling function also indicated the 2005-09-12 event as the period at which appreciable measure of energy from the solar wind gets into the magnetosphere.
  • The two striking events are clearly associated with dayside reconnection and auroral night-side substorm.
  • The dominant mechanism associated with the energization of the heavy ions is identified as the electron precipitation which, it is suggested, leads to the creation of an ambipolar electric field, an increase in the ion scale height and ion upwelling as a result.
  • Energy input from the solar wind through the dayside reconnection and night-side substorm is observed as additional means of heavy ion acceleration.
  • Upwelling of the heavy ion is significant when it is being influenced simultaneously by an enhancement in both electron temperature (through the precipitation flux) and ion temperature (through the Poynting flux).

My Research Findings

In summary, this research shows that heavy ions from the upper atmosphere, themselves produced by the solar wind interaction, are also responsible for slowing down the same space weather effects. This provides a great detail and help in developing our understanding of magnetospheric dynamics and consequently, a way to improve future magnetospheric modelling and perhaps, a way to approach the mitigation of space weather. 

It is worthy to point out that this work will take a look at spectral distribution over a period of time and consider the present events as case studies. Further investigation is on-going for a large dataset that would involve conjunction of ground based radars and spacecraft data, in order to have substantial events for a comprehensive statistical generalization.

About Timothy David

Timothy DavidTimothy David is a research student working towards completion of her doctoral degree in the Department of Physics and Astronomy. Timothy is supervised by Dr Darren Wright and Dr Steve Milan.

Timothy will present his work at the Festival of Postgraduate Research 6 July 2015 - see Timothy's Festival poster.

The Festival is open to all members of the University community and the public - book your place here.

Contact Timothy

Department of  Physics and Astronomy

University of Leicester

University Road

LEICESTER

LE1 7RH

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