The morning session began with Gareth

Chisham (British Antarctic Survey) in

the chair. Michele Dougherty (Imperial

College, London) took advantage of the

Cassini spacecraft flyby of Jupiter to carry out

simultaneous measurements of the solar wind

and Jovian magnetospheric conditions. She

reported the first observations of northward

Interplanetary Magnetic Field (IMF) condi-

tions leading to magnetopause erosion during

reconnection. Using previous spacecraft flights

through the Jovian current sheet, Jonathan

Nichols (Leicester) was able to deduce a model

of the planet’s magnetic field. He then com-

pared the resulting angular momentum and

auroral electron precipitation with those gen-

erated by a simple dipole magnetic field. It was

found that the self-consistent model was able

to account for the location and intensity of the

planet’s auroral oval.

Christina Pagel (Imperial College) examined

the heliospheric magnetic field observed

between the north and south poles during the

recent fast latitude scan of the Ulysses space-

craft. The level of magnetic fluctuations was

found to be greatest in the polar regions during

solar minimum and lower towards the solar

equator and at solar maximum. Holger

Schmitz (Warwick) made use of fully kinetic

particle-in-cell simulations of high Mach num-

ber shock waves to reveal a non-thermal

downstream electron energy distribution with

a high-energy tail in the bow shock of Mercury.

He found that electrons could become trapped

at the “foot” of the shock where they could

become accelerated by an electric field before

leaving the phase space hole.

Weak interplanetary shock waves

Several studies from Imperial College made use

of data from the Ulysses spacecraft. Jonathan

Gloag examined aspects of the detailed struc-

ture of weak interplanetary shock waves. He

observed behaviour that appeared to depart

from classical magnetohydrodynamic theory in

that there were often significant delays

between the times of the deflection of the

magnetic field and times of the change in the

magnitude of the field fluctuations. The unique

heliospheric polar orbit of Ulysses provided

Geraint Jones with data from a rapid 10-

month scan at both solar minimum and then

five years later at solar maximum (see figure 1).

During solar minimum, the dipolar solar mag-

netic field was clearly seen with a low-latitude

heliospheric current sheet. During 2001,

Ulysses sampled the Sun’s magnetic polarity at

all latitudes while it was undergoing a reversal.

Bogdan Hnat (Warwick) examined the statisti-

cal properties of the interplanetary magnetic

field. He found that a single scaling parameter

can describe its behaviour adequately on

timescales of less than 26 hours. Over longer

periods, the behaviour was more complex and

suggested a possible multifractal character.

Attention was shifted to the ionosphere by

Ranvir Dhillon (Leicester) as he described the

effect of varying the scanning angle of the

Tromsø ionospheric heater in the generation of

artificial backscatter in the CUTLASS Finland

HF radar. It was found that the power was

intensified in the direction along the Earth’s

magnetic field and that as the scan period was

reduced below a minute, there was a reduction

in the resulting backscattered power related to

the timescale of the excitation and decay

processes. Eoghan Griffin (University College

London) discussed the implications for the

thermosphere of observed small-scale structure

in the ionospheric convection flows and relat-

ed joule heating as observed by the CUTLASS

HF radar. He suggested that a high-resolution

Scanning Doppler Imager would complement

the ionospheric measurements in this region.

After lunch, Eleri Pryse (Aberystwyth) took

the chair. Richard Sims (Aberystwyth) present-

ed evidence for a “tongue of ionization” in

winter over Svalbard whereby cold plasma had

been transported from sub-auroral latitudes

into the polar cap during southward IMF con-

ditions. He made use of a range of ground-

and space-based instrumentation to show that

numerical models were not yet able to simulate

these phenomena. The first measurements of

F-region ion temperatures using a Fabry-Perot

interferometer were described by Mike Kosch

(Lancaster). Night-time singly ionized oxygen,

formed by auroral particle precipitation, pro-

vides the optical source. On three nights, there

was excellent agreement between the Euro-

pean Incoherent Scatter radar 300 km away

and the interferometer.

Chris Wilford (Sheffield) reported on

improvements to the Arecibo radar’s ability to

measure concentrations and temperatures of H+

and He+ up to altitudes of 2000 km. For the

first time it was possible to compare these val-

ues with in situ measurements from satellites.

These observations indicated significant layer-

ing of He+ around 700 km. Initial results from

the coupled thermosphere–ionosphere–plasma-

sphere (CTIP) model have been able to repro-

duce this feature. Jackie Davies (Leicester)

described joint EISCAT/CUTLASS radar obser-

vations of ionospheric signatures of dayside

transient reconnection. On the morning of 23

November 1999, the IMF was strongly south-

ward and a series of poleward-propagating

F-region electron density enhancements were

seen. These features appeared to originate from

around the open/closed field line boundary of

the magnetosphere/ionosphere system follow-

ing flux transfer events in the magnetosphere.

The magnetosphere from Cluster

The Earth’s magnetosphere, as seen by the

Cluster spacecraft, was the subject of the talk

by Jonathan Eastwood (Imperial). The behav-

iour of the magnetosheath region was com-

pared with conditions upstream in the solar

wind that were observed by the ACE space-

craft at the first Lagrangian point. Two mag-

netic field reversals took place on 13 February

2001 and statistical analysis techniques were

used to determine the evolution of the field

between the two spacecraft. Youra Taroyan

(Sheffield) was interested in the generation of

magnetohydrodynamic waves at the Earth’s

magnetopause. The existence of a finite non-

uniform layer between two semi-infinite homo-

geneous regions permitted several resonances

to occur. While Kelvin-Helmholtz instabilities

tended to favour high velocities, resonant flow

instabilities were found to become significant

at much lower flow speeds.

Kathryn McWilliams (Leicester) discussed a

magnetospheric flux transfer event that was

seen by the Geotail spacecraft as it passed

through the dawn magnetopause and its

impact on the ionosphere. The SuperDARN

network of HF radars was able to monitor the

convection flow conditions in the vicinity of

the spacecraft’s ionospheric footprint.

Changes in the orientation of the IMF during

this interval influenced the location of the

merging sites in the ionosphere. Silvia Dalla

(Imperial) examined the distribution of solar

energetic particles as seen from the two Helios

spacecraft within the Earth’s orbit and also

from the Ulysses spacecraft at a much greater

Meeting report

1.23February 2002 Vol 43

Autumn MISTThe annual one-day meeting of the MIST (Magnetosphere, Ionosphere and

Solar–Terrestrial) community was held on 23 November 2001 at the

Geological Society, Burlington House. Neil Arnold reports.

“…evidence for a tongue of

ionization in winter over

Svalbard … during southward

IMF conditions”

distance from the Sun. It was found that large

events of high energy coming from the Sun

take longer to decay at greater distances from

the Sun than would be predicted from theoret-

ical “magnetic bottle” models.

Magnetic cloud properties

The final session of the meeting was chaired by

Mike Kosch (Lancaster). A force-free flux rope

model was used by Adam Rees (Imperial) to

determine the gross properties of magnetic

clouds observed by Ulysses. Over the duration

of the mission so far, cloud properties were

sampled over a wide range of heliographic lat-

itudes and solar conditions. There appeared to

be preferred cloud orientations that were inde-

pendent of the latitude. Mathew Owens (Impe-

rial) analysed three years of solar wind data

from the ACE spacecraft to investigate the

relationship between magnetic field intensities

and solar wind speeds. He showed that the cor-

relation between the two quantities increased

as the threshold value of magnetic field inten-

sity was raised, indicating that some of the

high-speed and low-field observations may be

associated with off-axis flux ropes.

Keisuke Hosokawa (Kyoto and Leicester)

carried out an inter-hemispheric comparison of

spectral width boundaries as observed by the

SuperDARN radars. At equinox, the correla-

tion between the magnetic latitudes of these

conjugate boundaries is excellent and both

hemispheres show the same response to

magnetospheric reconnection. A difference of

10 minutes in the response time to a substorm

between the two radars used in the study can

be attributed to the effects of a significant

asymmetry in the IMF. Lisa Baddeley (Leices-

ter) reported the use of high-resolution artifi-

cial targets for the CUTLASS Finland HF

radar, generated by the high-power heater at

Tromsø, to observe high wave-number ULF

waves. Simultaneous observations from the

CAMMICE instrument on the Polar spacecraft

indicated a departure from a Maxwellian ion

distribution at 10 keV, consistent with energy

transfer from the particles to these waves via

the “drift-bounce” resonance process.

Cathryn Mitchell (Bath) described the

synthesis of multi-instrument total electron

content measurements to generate three-

dimensional “images” of the ionosphere.

Results from the USA and European regions

demonstrated the potential of imaging from

the auroral regions to the equator. During a

magnetic storm on 15 July 2000, an electron

density depletion over the European sector

was seen to extend down to 44°N. Sandra

Chapman (Warwick) rounded off the presen-

tations with a provocative talk about the use

of the statistics of extremal events to charac-

terize the game of football. It was found that

the top English league over the past 30 years

produced an uninteresting negative binomial

distribution, while worldwide domestic

leagues produced a long, non-Gaussian tail.

These techniques can be applied to the likeli-

hood of extreme events in plasma transport,

including the coupled Sun–Earth system. The

meeting concluded with thanks to all the con-

tributors and chairmen. �

Neil Arnold, University of Leicester. Note: much ofthe work reported on above is collaborative. Fullprogramme details, including titles, authors,abstracts and affiliations, may be found on theMIST Web pages at www.nerc-bas.ac.uk/public/uasd/mist.html.

Meeting report

1.24 February 2002 Vol 43

1: The polarity of theinterplanetary magneticfield at Ulysses mappedback to the Sun. The datawere recorded duringUlysses’ rapid scan fromthe southern to northernsolar polar regions duringsolar minimum in 1994–95(a) and solar maximum in2000–01 (b). The spheresshow the southern andnorthern hemispherescentred on Carringtonlongitudes of 0° (left) and180° (right), respectively.The solar minimumpolarities show the northernand southern hemispheresto be dominated by a singlemagnetic polarity. The dataobtained during solarmaximum record the morecomplex magnetic structureas magnetic polarityreversal was occurring.These latter data are thefirst ever to show magneticpolarities at highheliolatitudes around solarmaximum, and mayultimately provide importantclues to the behaviour ofthe solar dynamo.

(a)

(b)