4-2B
Magnetic variance data
The magnetic field around the earth changes. We want to correlate that change with
events related to the sun.
To observe changes in the magnetic field, you took measurements with your
magnetometer. Now, you can compare your numbers to changes measured by scientists.
Getting the magnetometer data online
The Tromso Geophysical Observatory data is available at:
http://geo.phys.uit.no/oldxdt2.html
Go to this website and select the Tromsø data and the date of interest. Click “Get it.!” A
graph will be displayed for the date you selected. Important dates should be included in
your final project results. For help interpreting the graphs, see the next page.
4-2B
Interpreting the graphs
The graph below is the graph from July 29th, 2002. Notice that there are three values
graphed. We will focus on the red graph.
The red graph shows the difference between geographic north and magnetic north
measured at this observatory. Notice that the y-axis values shown on the right and in red
are measured in degrees. Typically, magnetic north is a little over 3 degrees away from
geographic north as measured at Tromso (this magnetic variation, also called declination,
depends on location on the earth). However, magnetic north can “wander.” This graph
essentially shows how much the magnetic north has wandered.
Around 05 UT, the graph is above the flat line. The graph almost reaches a value of 4
degrees, meaning that geographic north and magnetic north are almost four degrees apart
as measured at Tromso. A few hours later, such as at 14 UT, the graph is closer to 3
degrees. Geographic north and magnetic north have gotten closer together as magnetic
north has changed location.
When interpreting the graphs and comparing to your data, be sure to convert the time to
match the East Coast time zone (see section below).
Universal time
U.T., or universal time, is the time in Greenwich. Depending on daylight savings time,
either subtract 4 or 5 hours from UT time and you will have the time in Boston.