ACE made measurements of Earth's dayside magnetosphere on August 25, 1997 as it crossed through different regions. It first passed through the inner magnetosphere, where the magnetic field follows a dipolar structure. It then entered the magnetosheath, where the field lines oscillate and run parallel to the solar wind. Finally, it crossed the bow shock into the interplanetary medium with a weak magnetic field exposed to the solar wind. The measurements confirmed the distinct magnetic properties of Earth's magnetosphere, magnetosheath, and interplanetary regions.

1. Probing the Dayside Magnetosphere:
Measurements by ACE soon after launch,
August 25, 1997
Travis Glines
Heather Briggs

2. Introduction
Launched on August 25, 1997
It crossed through:
the dayside magnetosphere
entered a region around the magnetosphere called the
magnetosheath (twice)
eventually crossed a weak bowshock into the
interplanetary medium exposed to the solar wind.
WIND was also making measurements.
The three regions of Earth's dayside magnetosphere
encountered by ACE are defined by different magnetic
properties as observed by our data.

3. Normal Dipole
The Earth's magnetic
field is nearly a dipole.
Figure 1 shows an ideal
dipole (as the Earth
would appear were it
unaffected by the sun).

4. Dipole Formula
r = L*cos2
(λ) is the equation for a dipole.
λ = Invariant latitude, the angle at which
the field leaves the earth's surface
L = the distance in Re at which a given
field line crosses the equatorial plane

5. Solar Influence

6. ACE Trajectory

7. Data collected of Dipole and Actual
The light line represents
the original dipole field
as obtained from the
previous formula
The dipole is evaluated
along the ACE trajectory
The dark line represents
the Earth's magnetic
field as measured by
ACE from 6 Re to 14 Re
The Earth's magnetic
field follows a dipolar
field until it enters the
magnetosheath.

8. The Three Regions of Earth's
Magnetic Environment
●
R1 is the inner regions
of our magnetosphere.
●
R2 is called the
magnetosheath, or the
outer boundary of our
magnetic field.
●
R3 is interplanetary
medium, separated
from our magnetic
field by a bow shock.

9. Region 1- The Magnetosphere
The magnetosphere is approximately a dipole in
which the field strength decreases at a rate of 1/r3
r represents the distance from Earth

10. Entering the Magnetosheath
The first dip shows where
ACE entered the
magnetosheath
The magnetic field then
expands to encompass the
satellite once again (the
forced re-entry)
The second major drop
showed the ACE
trajectory across the
magnetopause a second
time after being forced to
re-enter it

11. WIND Data
We compared this
solar wind data with
ACE's magnetic field
data
WIND noted a
pressure drop that had
repurcussions for
ACE half an hour
later and caused the
magnetosphere to then
recapture the
spacecraft

12. Region 2- The Magnetosheath
The field strength does
not depend on it's
distance from Earth.
The field lines
oscillate significantly.
The field lines run
parallel to the
interplanetary
magnetic field (IMF).
Average field strength
~ 10 nT

13. Region 3- Interplanetary Medium
The average field
strength of
Interplanetary Medium
is about 6 nT.
This graph shows a
field strength no
greater than 3 nT, thus
a weak field and bow
shock.

14. Bow Shock
The bow shock is a boundary area where the
interplanetary wind slows down to subsonic
speeds
This shock is produced when the wind slows
down and is thus diverted around the Earth so it
does not hit us head on
Our graph shows a weak bow shock due most
likely to the unusually low magnetic field
strength of the solar wind

15. Historical Viewpoint
The last time such an
analysis was
completed was in
1967
One of the earliest
was Explorer 12,
with much lower
time resolution.

16. Conclusion
Through ACE's measurements, we have verified
that the three specific regions associated with the
magnetosphere have difinitive properties singular
to those areas
In correlation with data obtained by WIND, we
have observed the effect of the solar wind on the
magnetosphere and verified that it is a fluctuating
boundary that is affected greatly by solar and
interplanetary radiation.

17. THE END