Overview

After successfully studying the low-latitude ionosphere and its response to equatorial irregularities for several years in the Pacific sector, we have branched out to perform a study in the American sector. Using the same field-aligned geometry originally proposed by Tinsley (JGR 1982), we are able to capture detailed images of the spatio-temporal development of these irregularities. The instruments (a PICASSO imaging system and two GPS-L1 scintillation monitors) are installed at the Cerro Tololo Inter-American Observatory (CTIO). CTIO, located east of La Serena, Chile (30.165 S, 70.815 W, 2215 m), houses a large 4-meter telescope and boasts some of the darkest skies and best seeing conditions in the world. For our work, we are observing the northern horizon, taking advantage of the high altitude and dark skies.

We plan to operate the equipment at CTIO for at least three years. We are also installing a similar suite of instruments in Colombia in the fall of 2006. In this way, we will have both footprints of the magnetic field lines over the Jicamarca Radio Observatory in Peru instrumented. It is our goal to study both how efficiently structure at different scale-sizes map from the magnetic equator to the low-latitude ionosphere and what control the local ionosphere has on the severity of the effects of the irregularities.

Data from this project are posted to our online database. We are happy to collaborate with interested scientists. Please contact Prof. Makela with any questions.

Instruments

The suite of instruments installed at CTIO consist of a Portable Ionospheric Camera and Small Scale Observatory (PICASSO) system and two GPS-L1 scintillation monitors. Together, these instruments will shed light on the types of structures present in the ionosphere over CTIO and provide quantitative information on scale-sizes and drift velocities of scintillation causing ionospheric irregularities.

PICASSO
To install the PICASSO system, we had a hole cut into the side of the airglow building at CTIO. Because we are interested in viewing towards the northern horizon, we required a site that would provide us an unobstructed view. We also required a fast connection to the internet to be able to download our data for analysis back at the University of Illinois. One of the advantages of the PICASSO system is its small size, making installation significantly easier than previous ionospheric imaging systems, which required significantly more infrastructure to support. In the case of this installation, we had a simple shelf constructed which house the imaging system and all of the associated electronics (laptop computer, hard drives, and liquid cooling unit).

The specific PICASSO system that we installed at CTIO was of the narrow-field variety. Rather than observing from horizon to horizon, the field of view is limited to approximately 50 degrees. As a consequence of this reduction in the field of view, the spatial resolution we achieve is much improved; in the current imaging mode, we obtain sub-km spatial resolution. The system has three filters for observing specific emissions of interest (two for science, one to observe the continuum background). Depending on conditions and the details of what types of events we are trying to study, we operate the system in different modes.

SCINTMON
In addition to the PICASSO system, we installed two GPS-L1 scintillation monitors developed at Cornell University. This installation consisted of setting up two antennas separated in the magnetic east-west direction by approximately 25 meters. By comparing the temporal variations of the signals obtained by these two antennas, we can infer the drift velocity of the structures causing the variations. These systems are also connected to the internet, allowing us to monitor activity on a real-time basis.

We were fortunate to capture some interesting events events within the first week of operation. The example shown here demonstrates the type of structures we are studying in relation to equatorial irregularities. The image was captured using the 630.0-nm filter and clearly shows a well developed equatorial plasma bubble. In addition to the main plume, there is also evidence of several secondary plumes having developed. This particular example did not exhibit any effects on the GPS system, primarily due to the low electron density during the southern hemisphere winter months at solar minimum. We expect that the densities will become larger as we head toward southern hemisphere summer months and solar maximum. An example movie created from an entire night's worth of data, showing the spatial and temporal dynamics of these structures can be found here.

Collaborators

This project is sponsored by the National Science Foundation. The building that the instruments are housed in is operated by our colleagues at Scientific Solutions, Inc and maintained by the staff at the Cerro Tololo Inter-American Observatory. We would like to thank the staff at CTIO who were tremendously helpful in installing and maintaining the equipment.The GPS scintillation monitors were provided by the GPS Laboratory run by Prof. Paul Kintner of Cornell University and are operated by Dr. Brent Ledvina.